BEIRUT -- Syrian rebels on Saturday seized a major air defense base in a strategic region of southern Syria near the Jordanian border in the latest battlefield triumph for fighters seeking to topple President Bashar Assad, activists said.

Fighters with a rebel group active in the south stormed and seized control of the air defense base used by the 38th Division after a 16-day siege, according to a statement posted on websites of the group known as the Yarmouk Martyrs Brigade.

The base near the village of Saida is situated along the international highway linking the Syrian capital, Damascus, with Jordan to the south.

Fighting in Syria's southern provinces bordering Jordan and Israel has increased sharply in the past few days. The Syrian Observatory for Human Rights said dozens of people, mostly opposition fighters, were killed in heavy clashes this week in the Quneitra region along the cease-fire line between Syria and Israel in the Golan Heights.

The Britain-based group, which relies on a network of activists on the ground, said it had documented the deaths of 35 opposition fighters and the loss of contact with more than 20 others believed to have died in the fighting. Dozens of others were wounded, the group said.

The fighting in the area intensified midweek after rebels seized a village and parts of other villages, closing in on the strategic plateau that Israel captured from Syria in 1967 and later annexed.

If the rebels take over the Quneitra region, it will bring radical Islamic militants to a front line with Israeli troops. The rebel force comprises dozens of groups, including the powerful al-Qaida-linked Jabhat al-Nusra, which the Obama administration labels a terrorist organization.

The Observatory said al-Nusra was among fighters who seized the air defense base in Daraa province. Both the rebels and the observatory reported that the opposition fighters killed the base commander.

In Damascus, supporters of Assad gathered in downtown amid tight security for the funeral of one of Syria's best-known clerics who was assassinated in a brazen mosque bombing earlier this week.

Security forces sealed off all roads leading to the eighth century Omayyad Mosque where the funeral for Sheik Mohammad Said Ramadan al-Buti, an 84-year-old pro-government cleric, was held.

Al-Buti, his grandson and 48 others were killed Thursday when a suicide bomber detonated his explosives inside a mosque where al-Buti was giving a religious lesson.

His assassination was a blow to Assad, who vowed Friday to avenge his death, saying he would "purge" the country of the militants behind the attack in the heart of the capital.

Both Assad and the rebels seeking to topple him have blamed each other for the bombing at the mosque.

Al-Buti, the most prominent religious figure killed so far in the 2-year-old conflict, had supported the regime since the early days of Assad's father and predecessor, the late President Hafez Assad, providing legitimacy to their rule. Sunnis are the majority sect in Syria while Assad is from the minority Alawite sect - an offshoot of Shiite Islam.

Mourners carried al-Buti and his grandson's coffins, draped in white cloth, on their shoulders amid shouts of "God is Great."

Al-Buti was imam of the Omayyad Mosque, a landmark in Damascus. Church bells tolls and mosque minarets in the ancient city blared "God is Great" during the funeral procession.

Syrian state TV said Assad was being represented at the funeral by one of his cabinet ministers.

Al-Buti was being buried in a courtyard at the rear of the mosque near the tomb of Saladin, a medieval Muslim ruler.

In a show of support, a delegation from the Lebanese Shiite Muslim Hezbollah group, a staunch ally of Assad, drove to Damascus for the funeral. A delegation from Iran was also present.

"We will continue on the same path," said Sheik Mohammed Yazbeck, a member Hezbollah's highest decision-making body, the Shura Council. "We will return the blow to the enemies of Syria and the enemies of the nation," he added.

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Associated Press Writer Albert Aji contributed to this report from Damascus.

Earlier on HuffPost:

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  • March 2011: 120

    Thousands of Syrians rally to show their support for President Bashar al-Assad, who is facing unprecedented domestic pressure amid a wave of dissent, in Damascus on March 29 2011. (ANWAR AMRO/AFP/Getty Images)

  • April 2011: 820

    A protestor burns a portrait of Syrian President Bashar al-Assad during a demonstration after Friday prayers on April 29 2011 in Istanbul against the regime of al-Assad and the deadly crackdown on opposition protests. (BULENT KILIC/AFP/Getty Images)

  • May 2011: 850

    A veiled woman takes part in a protest calling on Syria's President Bashar Assad to step down, in front of the United Nations headquarters in Amman, on May 21 2011. (KHALIL MAZRAAWI/AFP/Getty Images)

  • June 2011: 1,000

    Syrian refugees arrive to a makeshift camp in the northern city of Idlib, in Syria, on June 13 2011. (MUSTAFA OZER/AFP/Getty Images) <em><strong>CORRECTION:</strong> An earlier version of this caption placed the city of Idlib in Turkey. Idlib is in Syria. </em>

  • July 2011: 1,600

    Thousands of pro-regime Syrians wave their national flag and portraits of President Bashar al-Assad during a rally in Damascus on July 17 2011. (LOUAI BESHARA/AFP/Getty Images)

  • August 2011: More than 2,000

    People hold pictures of Syrian president Bashar al-Assad and fallen Libyan strongman Muammar Gaddafi as they take part in a demonstration gathering activists opposed to Syria's regime of President Bashar al-Assad on August 28 2011 at Taksim Square in Istanbul. (BULENT KILIC/AFP/Getty Images)

  • September 2011: 2,700

    A national flag hangs on a statue of Syria's late president Hafez al-Assad at the entrance of the flashpoint city of Homs on August 30 2011, as rights activists reported widespread anti-regime protests across Syria on the first day of the feast marking the end of Ramadan. (JOSEPH EID/AFP/Getty Images)

  • October 2011: 3,000

    Supporters of Syrian President Bashar al-Assad wave Syrian flags during a pro-regime rally in Damascus on October 12, 2011. Assad's regime is facing international pressure amid a violent crackdown on anti-government protests that broke out in March across Syria. (LOUAI BESHARA/AFP/Getty Images)

  • November 2011: More than 4,000

    Syrian soldiers carry on November 26, 2011 the coffin of a comrade reportedly killed in an ambush by an armed group in the flashpoint Syrian city of Homs. (AFP/Getty Images)

  • December 2011: More than 5,000

    Free Syrian Army captain identified as Ahmed al-Arabi sits in a safe house near Wadi Khaled on the Lebanese-Syrian border on December 30 2011. (Si Mitchell/AFP/Getty Images)

  • January 2012: 7,100

    Free Syrian Army fighters take position in a house on the Lebanese-Syrian border prior to a nighttime operation on January 2 2012. (Si Mitchell/AFP/Getty Images)

  • February 2012: 7,500

    A Turkish journalist in Ankara, holds pictures of two journalists, French photojournalist Remi Ochlik and Sunday Times correspondent Marie Colvin, killed in an alleged rocket attack by Syrian regime forces against a makeshift opposition media center in the besieged city of Homs in Syria on February 22 2012. (ADEM ALTAN/AFP/Getty Images)

  • March 2012: More than 8,000

    A defected Syrian soldier, now a member of the Free Syrian Army, stands outside a mountain outpost near the village of Janudieh in the northern province of Idlib on March 20 2012. (STR/AFP/Getty Images)

  • April 2012: Close to 9,000

    Syrians pray over the bodies of Syrian violence victims at a funeral in the northwestern town of Kafr Zeta on April 10, 2012. (AFP/Getty Images)

  • May 2012: More than 9,000

    A general view shows the Syrian flag flying next to destruction in the Bab Amro neighbourhood of Homs on May 2 2012. (JOSEPH EID/AFP/GettyImages)

  • June 2012: 14,000

    A Syrian man carries a wounded girl next to Red Crescent ambulances following an explosion that targeted a military bus near Qudssaya, a neighbourhood of the Syrian capital, on June 8, 2012. (AFP/GettyImages)

  • July 2012: 19,000

    Members of Jihadist group Hamza Abdualmuttalib train near Aleppo on July 19, 2012. Rebels seized control of all of Syria's border crossings with Iraq on July 19. (BULENT KILIC/AFP/GettyImages)

  • August 2012: 23,000

    A Syrian boy whose family has been displaced due to fighting between rebel fighterws and Syrian government forces is seen near the Syrian border with Turkey on August 25, 2012. (ARIS MESSINIS/AFP/GettyImages)

  • September 2012: 30,000

    A Syrian man carrying grocery bags tries to dodge sniper fire as he runs through an alley near a checkpoint manned by the Free Syria Army in the northern city of Aleppo on September 14, 2012. (MARCO LONGARI/AFP/Getty Images)

  • October 2012: 36,000

    A Syrian boy plays on a destroyed tank near the rubble of a mosque that was destroyed during fighting between Syrian rebels and regime forces in the northern city of Azaz on September 23, 2012. (MIGUEL MEDINA/AFP/GettyImages)

  • November 2012: 40,000

    A walnut tree stripped of its branches stands in the rubble of the Kalat al-Numan citadel, originally built during the Roman era some 2000-years-ago, after allegedly being bombed several times by the Syrian air force on November 18, 2012, in Maaret Al-Numan in southern Idlib province. (John Cantlie/AFP/Getty Images)

  • December 2012: 60,000

    Smoke rises in the Hanano and Bustan al-Basha districts in the northern city of Aleppo on December 1, 2012 as fighting continues through the night. (Javier Manzano/AFP/Getty Images)

  • January 2013: 65,000

    A boy plays with a balloon in a Syrian refugees camp in Azaz, near the Turkish border, on January 10, 2013 after snow falls. (EDOUARD ELIAS/AFP/Getty Images)

  • February 2013: More than 70,000

    Syrian Zakia Abdullah sits on the rubble of her house in the Tariq al-Bab district of the northern city of Aleppo on February 23, 2013. (Pablo Tosco/AFP/Getty Images)