BEIRUT — Rebels backed by captured tanks launched a fresh offensive on a government complex housing a police academy near the northern city of Aleppo on Sunday, while the government hit back with airstrikes to try to protect the strategic installation, activists said.

If rebels capture the complex on the outskirts of Aleppo, it would mark another setback for President Bashar Assad. In recent weeks, his regime has lost control of key infrastructure in the northeast including a hydroelectric dam, a major oil field and two army bases along the road linking Aleppo with the airport to its east.

Rebels also have been hitting the heart of Damascus with occasional mortars shells or bombings, posing a stiff challenge to the regime in its seat of power.

On Saturday, opposition fighters in the eastern province of Deir el-Zour overran a military post believed to have once been the site of a partly built nuclear reactor that Israeli warplanes bombed in 2007.

A year after the strike, the U.N. nuclear watchdog determined that the destroyed building's size and structure fit specifications of a nuclear reactor. Syria never stated the purpose of the site known as Al-Kibar.

After the bombing, the regime carted away all the debris from the destroyed building and equipment from the two standing structures, analysts said, adding that the rebels were unlikely to have found any weapons in the abandoned complex.

There were troops in the area until this weekend. It was not clear what the site was being used for most recently.

"It's more or less a shell because the Syrians decided to remove everything inside the buildings," said Mustafa Alani, an analyst with the Gulf Research Center in Geneva. "I don't think there's anything left really of any value for the rebels."

Separately, rebels have been trying for months to storm the government complex west of Aleppo in the suburb of Khan al-Asal, according to Rami Abdul-Rahman, the director of the Britain-based Syrian Observatory for Human Rights.

The facility also includes several smaller army outposts charged with protecting the police academy inside the compound.

The SANA state news agency said regime troops repelled the rebel attack on the police academy, inflicting heavy losses and destroying four armored vehicles and three cars fitted with machine guns. There was no word on government casualties.

Aleppo has been the scene of some of the heaviest fighting of Syria's nearly 2-year-old conflict.

In July, rebels launched an offensive on the city, the country's largest and one-time commercial capital, and quickly seized several neighborhoods. The battle has since devolved into a bloody stalemate, with heavy street fighting that has left whole districts in ruins and forced thousands to flee.

A key focus for the rebels as they try to capture the city is Aleppo's international airport, which they have been attacking for weeks.

Regime forces also fired an apparent ground-to-ground missile Sunday on the town of Tal Rifat, some 30 kilometers (20 miles) north of Aleppo, the Observatory said. There was no immediate word on casualties.

The report follows similar strikes last week on impoverished rebel-held Aleppo neighborhoods that killed at least 60 people.

Also on Sunday, prominent Syrian comedian Yassin Bakoush was killed in Damascus after apparently being caught in the crossfire between rebels and government troops.

Bakoush, 75, was known for playing characters that were likeable but naive and dim-witted. SANA said he is survived by11 children.

SANA said Yassin Bakoush was killed by a rebel mortar round that landed on his car in the Yarmouk Palestinian refugee camp in southern Damascus, which has seen heavy fighting in recent months. However, the anti-regime Observatory said Bakoush was killed when a rocket-propelled grenade launched by government forces slammed into his car.

French freelance photographer Olivier Voisin, who was wounded on Thursday in Syria and taken to Turkey for treatment, died of his wounds at an Istanbul hospital, the French Foreign Ministry said Sunday.

Voisin is the second French journalist this year to be killed while reporting on the civil war, which has proven to be one of the most dangerous conflicts for reporters to cover.

In Lebanon, two people were killed by Syrian shells and gunfire that landed on Lebanese territory near the border.

The state-run National News Agency in Lebanon said a man was killed and his brother was wounded by shells that slammed into the town of al-Hisheh in the Wadi Khaled area of the north, while another man was killed by gunfire in the area of al-Buqaiaa.

The deaths added to tensions in the area which has seen an escalation of violence in recent days. The civil war in Syria has increasingly spilled over into Lebanon with almost daily reports of cross-border shelling or gunfire in border areas.

The United Nations says at least 70,000 people have been killed since the uprising against Assad's authoritarian rule began nearly two years ago.

Efforts to stop the bloodshed so far have failed, leaving the international community at a loss of how to end the civil war.

A senior opposition leader said Sunday that his umbrella group has suspended participation in meetings with its Western backers and their Arab allies because of their indifference over the regime's attacks on the Syrian people in Aleppo and other cities.

"Assad has reached the stage of real genocide amid Arab silence and we renounce that," George Sabra, vice president of the Syrian National Coalition, said in Cairo after meeting Arab League chief Nabil Elaraby.

On Friday, the Coalition said its leaders would not travel to Washington or Moscow for any talks to protest the international community's "silence over crimes committed by the regime." It also said opposition leaders would boycott a meeting next month in Rome of the Friends of Syria, which includes the United States and its European allies.

In Washington, the State Department condemned rocket attacks on Aleppo, saying in a statement late Saturday the strikes are the "latest demonstrations of the Syrian regime's ruthlessness and its lack of compassion for the Syrian people it claims to represent."

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Associated Press writers Ryan Lucas in Beirut and Lori Hinnant in Paris contributed to this report.

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  • Turkey

    Turkey has struck the Syrian military repeatedly in response to shelling and mortar rounds from Syria since Oct. 3, when shells from Syria struck the Turkish village of Akcakale, killing two women and three children. The incident prompted NATO to convene an emergency meeting and Turkey sent tanks and anti-aircraft batteries to the area. Turkey's military has also scrambled fighter jets after Syrian helicopters flew close to the border. <em>Caption: Turkish soldiers patrols as Syrian nationals pass the border between Syria and Turkey on November 10, 2012, near the town of Ceylanpinar. (BULENT KILIC/AFP/Getty Images)</em>

  • Turkey

    There are about 120,000 Syrian refugees sheltering in Turkish camps, with up to 70,000 more living in Turkey outside the camps. Thousands more wait at the border, held up as Turkey struggles to cope with the influx. Turkey also hosts much of the opposition and rebel leadership. <em>Caption: A Syrian-Kurdish woman refugee sits in the courtyard of a house in the Turkish town of Ceylanpinar, bordering Syria, on November 10, 2012. (PHILIPPE DESMAZES/AFP/Getty Images)</em>

  • Turkey

    Turkey has called for a buffer zone in Syria where the opposition and civilians would be protected, a step that would likely require international enforcement of a no-fly zone. Russia and China have blocked robust moves against the Syrian regime at the U.N. Security Council, and the United States has been reluctant to use its military in another Mideast conflict. <em>Caption: Turkish soldiers patrols as Syrian nationals pass the border between Syria and Turkey on November 10, 2012, near the town of Ceylanpinar. (BULENT KILIC/AFP/Getty Images)</em>

  • Israel

    Israel on Monday became the second country to strike the Syrian military, after Turkey. An Israeli tank hit a Syrian armored vehicle after shells from fighting in Syria exploded in Israel-controlled Golan Heights. A day earlier, Israel fired a warning shot near a group of Syrian fighters. <em>Caption: Israeli tanks, one in position, the other getting into a firing position in the Israeli-controlled Golan Heights overlooking the Syrian village of Bariqa, Monday, Nov. 12, 2012. (AP Photo/Ariel Schalit)</em>

  • Israel

    Syrian shells have exploded inside the Golan several times in recent weeks damaging apple orchards, sparking fires and spreading panic but causing no injuries. In early November, three Syrian tanks entered the Golan demilitarized zone, and in a separate incident an Israeli patrol vehicle was peppered with bullets fired from Syria; no one was hurt in the incident and the Israeli military deemed it accidental. <em>Caption: Smoke rises after shells fired by the Syrian army explode in the Syrian village of Bariqa, Monday, Nov. 12, 2012. (AP Photo/Ariel Schalit)</em>

  • Israel

    There is concern in Israel that Assad may try to spark a conflict with Israel, opening up the potential for attacks by Lebanon's militant Hezbollah and Hamas in the Gaza Strip. Israel has also warned that Syria's chemical weapons could be turned on the Jewish state. Still, while no friend of Assad, Israel is also worried that if he is toppled, Syria could fall into the hands of Islamic extremists or descend into sectarian warfare. <em>Caption: Israeli troops and UN peacekeepers inspect on November 8, 2012 the area where three mortar shells fired from Syria landed in Alonei Habashan in the Israeli-occupied Golan Heights, which Israel seized from Syria in 1967. (JALAA MAREY/AFP/Getty Images)</em>

  • Lebanon

    Mortars and shells from the Syrian side regularly crash in Lebanon, causing several casualties, though Lebanese forces have never fired back. More dangerously, Syria's conflict has heightened deep rivalries and sectarian tensions in its smaller neighbor. Lebanon is divided between pro-Assad and anti-Assad factions, a legacy of the nearly three decades when Damascus all but ruled Lebanon, until 2005. Assad's ally, the Hezbollah militia is Lebanon's strongest political and military movement. <em>Caption: Lebanese army commandos deploy in the Bab al-Tabbaneh and Jabal Mohsen neighbourhoods where clashes are taking place between Sunnis and Alawites in the northern city of Tripoli on October 23, 2012. (JOSEPH EID/AFP/Getty Images)</em>

  • Lebanon

    On Oct. 19, a car bomb assassinated Lebanon's top intelligence chief, Wissam al-Hassan. Many in Lebanon blamed Syria and Hezbollah for the assassination. The northern Lebanese city of Tripoli has seen repeated clashes between Sunni Muslims and Alawites – the Shiite offshoot sect to which Assad belongs. Battles in the city in May and August killed at least 23 people total and wounded dozens. <em>Caption: A memorial poster of Brig. Gen. Wissam al-Hassan, who was assassinated Friday, hangs near the spot Friday's car bomb attack that killed Al-Hassan, in the Achrafieh district of Beirut, Lebanon, Tuesday, Oct. 23, 2012. (AP Photo/Maya Alleruzzo)</em>

  • Lebanon

    The kidnapping of Lebanese Shiites in Syria by rebels has also had repercussions in Lebanon. In May, Shiites blocked roads and burned tires in protest over the abductions, and later in the summer a powerful Shiite clan took 20 Syrians and a Turk in Lebanon captive in retaliation, all of whom have since been released. Lebanon also shelters about 100,000 Syrian refugees. <em>Caption: A Syrian man Firas Qamro, 31, who was injured during clashes that erupted between supporters and opponents of the Syrian regime, in the northern port city of Tripoli, Lebanon, Monday, Oct. 22, 2012. (AP Photo/Bilal Hussein)</em>

  • Jordan

    Jordan has taken the brunt of the refugee exodus from Syria, with some 265,000 Syrians fleeing across the border. Around 42,000 of them are housed at Zaatari, a dust-filled refugee camp, where riots have broken out several times by Syrians angry over lack of services. A growing number of stray Syrian missiles have fallen on Jordanian villages in the north in recent weeks, wounding several civilians. <em>Caption: In this Saturday, Sept. 15, 2012 photo, a Jordanian army vehicle carries Syrian refugees who have fled violence in their country having crossed into Jordanian territory with their families near the town of Ramtha. (AP Photo/Raad Adayleh)</em>

  • Jordan

    Late last month, a Jordanian border patrol officer was killed in clashes with eight militants trying to cross into Syria. Hours earlier, Jordan announced the arrest of 11 suspected al-Qaida-linked militants allegedly planning to attack shopping malls and Western diplomatic missions in Jordan. <em>Caption: Jordanian border soldiers guard newly-arrived Syrian refugee families after they crossed the border from Tal Shehab city in Syria, through the Al Yarmouk River valley, into Thnebeh town, in Ramtha , Jordan, Wednesday, Sept. 5, 2012. (AP Photo / Mohammad Hannon)</em>

  • Iraq

    Sunni and Shiite fighters from Iraq have made their way to Syria to join the civil war – the former on the side of the opposition, the latter siding with Assad's regime, according to Iraqi officials and Shiite militants. Sunni al-Qaida fighters are believed to be moving between Iraq and Syria, and some al-Qaida fighters in Iraq's western Anbar province have regrouped under the name of the Free Iraqi Army, a nod to the rebels' Free Syrian Army, Iraqi officials say. <em>Caption: In this Saturday, March 17, 2012 file photo, Syrian security officers gather in front the damaged building of the aviation intelligence department, which was attacked by one of two explosions in Damascus, Syria. (AP Photo/Bassem Tellawi, File)</em>

  • Iraq

    About 49,000 Syrian refugees have temporarily resettled in Iraq, according to the U.N. refugee agency. The United States has pressured Baghdad to stop Iranian planes suspected of ferrying arms to Syria from using Iraqi airspace. Iraq has so far acknowledged only forcing two planes to land for inspection and said it didn't find any weapons either time. <em>Caption: Syrian refugees rest as they have crossed the border by the Iraqi town of Qaim, 200 miles (320 kilometers) west of Baghdad, Iraq, Tuesday, Aug. 7, 2012. (AP Photo/Hadi Mizban)</em>