By Erika Solomon
AZAZ, Syria, July 28 (Reuters) - Military helicopters pounded a rebel-held district of Aleppo on Saturday and armoured units positioned themselves for an onslaught that could determine the fate of Syria's biggest city, opposition sources said.
Turkey, once a friend but now a fierce critic of the Syrian government, joined growing diplomatic pressure on President Bashar al-Assad, calling for international steps to deal with the military build-up.
The Syrian Observatory for Human Rights, an opposition group which collects information on the 16-month-old uprising against Assad, reported helicopter attacks on the central Salaheddine district of Aleppo and fighting elsewhere in the city.
"Helicopters are participating in clashes at the entrance of Salaheddine district and bombarding it," the group said in an emailed statement. "There are also violent clashes at the entrances to Sakhour district."
One opposition activist said he had seen Syrian tanks and armoured carriers heading for Salaheddine.
The battle for the city of 2.5 million people is seen as a crucial test for a government that has committed major military resources to retaining control of its two main power centres, Aleppo and the capital Damascus, in the face of a growing insurgency.
While neither side has managed to gain the upper hand, the outcome of the uprising is being watched anxiously in the region and beyond, amid fears that sectarian unrest could spread to volatile neighbouring countries.
Military experts believe that while Assad's more powerful military will overcome the rebels in Aleppo and other major cities, it risks loss of control in the countryside because the loyalty of large sections of the army is in doubt.
"Assad's forces are likely to achieve a tactical victory that will represent a setback to opposition forces and allows the regime to demonstrate its military dominance," said analyst Ayham Kamel of the Eurasia Group, adding however that the rebels were getting stronger while the military was on the wane.
Three rebel fighters were killed in clashes before dawn on Saturday in Aleppo, the Observatory said. It said 160 people were reported killed in Syria on Friday, adding to an overall death toll of around 18,000 since the uprising began.
Video footage provided by the Observatory showed smoke rising over apartment blocks in the city into a hazy sky on Saturday. The sound of sporadic gunfire could be clearly heard.
While attention has focussed on Aleppo, fighting was also reported in towns across Syria: Deraaa, the cradle of the revolution, Homs, the scene of some of the bloodiest combat, and Hama, where a revolt against Assad's father in the early 1980s was suppressed with thousands of deaths.
At least 10 people were killed on Saturday when Syrian security forces went into Maadameyat al-Sham near Damascus, the observatory said.
TURKEY CALLS FOR ACTION
Turkish Prime Minister Tayyip Erdogan said late on Friday that international institutions needed to work together to address the military assault on Aleppo and Assad's threat to use chemical weapons against external enemies.
"There is a build-up in Aleppo, and the recent statements with respect to the use of weapons of mass destruction are actions that we cannot remain an observer or spectator to," he said at a news conference in London with British Prime Minister David Cameron.
"Steps need to be taken jointly within the United Nations Security Council, the Organisation of Islamic Countries, the Arab League, and we must work together to try to overcome the situation," he said.
Earlier, Erdogan had cheered on the rebels.
"In Aleppo itself the regime is preparing for an attack with its tanks and helicopters ... My hope is that they'll get the necessary answer from the real sons of Syria," he told Turkish TV.
Cameron said Britain and Turkey were concerned that Assad's government was about to carry out some "some truly appalling acts around and in the city of Aleppo".
Russian said that international support for Syrian rebels would lead to "more blood" and the government could not be expected to willingly give in to its opponents.
Foreign Minister Sergei Lavrov, whose country has vetoed three U.N. Security Council resolutions intended to increase pressure on Assad, said Western and Arab nations should exert more influence on rebels to stop fighting.
Russia also said it would not allow searches of Russian-flagged ships under new European Union sanctions governing vessels suspected of carrying weapons to Syria.
U.N. rights chief Navi Pillay urged both Syrian government forces and rebels on Friday to spare civilians in Aleppo, voicing deep concern at the "likelihood of an imminent major confrontation" in the city reminiscent of other deadly assaults.
United Nations Secretary-General Ban Ki-moon said he was deeply concerned about reports that Syria could use chemical weapons and demanded that the government should state it would not use them "under any circumstances".
But the White House said such a promise from the Syrian president was "certainly not enough" given Assad had paid only lip service to a U.N.-backed peace plan.
"Assad's word is not worth very much," White House spokesman Jay Carney said. "Any use of those weapons, any failure to safeguard those stockpiles would be a very serious transgression that would result in those responsible being held accountable."
In stating this week that it would not use chemical weapons against its own people, but might do so against external threats, Syria caused major international concern about its stockpiles of non-conventional weapons.
The increase in fighting in Aleppo follows a bomb attack on July 18 that killed Assad's defence minister and three other top officials in Damascus, a development that led some analysts to speculate that the government's grip was slipping.
Since then, Assad's forces have mounted a strong counter-attack against rebels in Damasacus as well as concentrating forces for an expected assault on Aleppo.
09/09/2012 12:25 PM EDT
Syria Blasts Aleppo By Air
09/05/2012 7:50 AM EDT
Syrian City In Flames
08/25/2012 1:45 PM EDT
Lebanese Pilgrim Freed
Hussein Ali Omar, 60, one of 11 Lebanese Shiite pilgrims that Syrian rebels have been holding for three months in Syria, hugs his mother, right, upon arrival at his house in the southern suburb of Beirut, Lebanon, 2012. Syrian rebels freed Omar on Saturday in a move aimed at easing cross-border tensions after a wave of abductions of Syrian citizens in Lebanon. The Shiite pilgrims were abducted May 22 after crossing into Syria from Turkey on their way to Lebanon. (AP Photo/Hussein Malla)
08/24/2012 12:22 PM EDT
This image made from video and released by Shaam News Network and accessed Thursday, Aug. 23, 2012, purports to show the funeral of children in Daraya, near Damascus, Syria. Syrian troops backed by tanks and helicopters broke into a Damascus suburb on Thursday following two days of shelling and intense clashes as part of a widening offensive by President Bashar Assad's forces to seize control of parts of the capital and surrounding areas from rebel fighters, activists said. At least 15 people were killed in the offensive on Daraya, only a few miles (kilometers) southwest of Damascus. (AP Photo/Shaam News Network SNN via AP video)
08/24/2012 11:05 AM EDT
Lebanon Sees Heaviest Clashes In Months
Clashes between Assad supporters and opponents of the Syrian regime killed two people in Lebanon on Friday, the Associated Press reports. 17 people were injured.
The AP gives more context:
Syria was in virtual control of its smaller neighbor for many years, posting tens of thousands of troops in Lebanon, before withdrawing under pressure in 2005. Even without soldiers on the ground, Syria remains influential, and its civil war has stirred longstanding tensions that have lain under Lebanon's surface.
Read more on HuffPost World.
08/24/2012 11:02 AM EDT
A Sunni gunman fires a gun during clashes that erupted between pro and anti-Syrian regime gunmen in the northern port city of Tripoli, Lebanon, Friday, Aug. 24, 2012. The latest round of fighting first erupted on Monday in northern Lebanon and at least 15 have been killed in Tripoli this week and more than 100 have been wounded in fighting that is a spillover from Syria's civil war. (AP Photo/Hussein Malla)
08/24/2012 11:00 AM EDT
Refugee Numbers Soar
@ KenRoth :
UN reports 200,000 #Syria refugees, 30,000 in past week alone. Many more internally displaced not counted. http://t.co/BaM6u59j
08/23/2012 2:00 PM EDT
Syrian boy Musataf Alhafiz, 11, who fled his home with his family due to fighting between the Syrian army and the rebels, carries his brother Saif, 9 months, while he and others take refuge at the Bab Al-Salameh border crossing, in hopes of entering one of the refugee camps in Turkey, near the Syrian town of Azaz, Thursday, Aug. 23, 2012. Thousands of Syrians who have been displaced by the country's civil war are struggling to find safe shelter while shelling and airstrikes by government forces continue. (AP Photo/Muhammed Muheisen)
08/23/2012 12:09 PM EDT
Heaviest Bombardment This Month
Helicopter gunships shelled Damascus on Wednesday as Syrian security forces intensified their assault on the capital. Activists report that at least 47 people were killed.
"The whole of Damascus is shaking with the sound of shelling," a woman in the neighborhood of Kfar Souseh told Reuters.
Read more on HuffPost World.