Heavy fighting resumed in eastern Aleppo on Wednesday, including airstrikes, shelling and gunfire, the Britain-based Syrian Observatory for Human Rights, rebel groups and witnesses said. The renewed violence signals a major delay in evacuations and a possible collapse of a ceasefire deal between the Syrian opposition and forces aligned with the Syrian government.

"The clashes are violent and bombardment is very heavy ... it seems as though everything (the ceasefire) is finished," Rami Abdurrahman, director of the monitoring group, said. The group added that the airstrikes were carried out by Syrian government aircraft.

An AFP news agency correspondent saw several wounded civilians as the area came under heavy tank fire. Rebel fire reportedly killed six people, according to Syrian state television.

Zouhir Al Shimale, a journalist located in eastern Aleppo, tweeted that "dozens" of people were killed in the latest shelling, including women and children.

Buses meant to evacuate rebels and tens of thousands of civilians from eastern Aleppo left evacuation pick-up points and returned to their depots, according to media reports. 

Russia's Defense Ministry, meanwhile, said that the rebels resumed fighting at dawn and that the Syrian government forces subsequently repelled their attacks, the Interfax news agency reported.

The ministry said a convoy of buses meant to transport civilians in the Salaheddin neighborhood came under fire from rebel territory. Russia's military said the rebel fighters were attempting to break through government positions, but said the Syrian army "warded off" the attack and continued its operation to "liberate" eastern Aleppo.

Truce deal in trouble

The ceasefire deal to allow for evacuations of opposition fighters and thousands of civilians was reached late on Tuesday after negotiations between Turkey and Russia.

Turkish President Recep Tayyip Erdogan said on Wednesday he would call Russian President Vladimir Putin in an attempt to rescue the deal.

"I will speak with Mr Putin again later in the evening," Erdogan said during a televised speech. "The situation on the ground is very fragile and complicated."

Rebels said the government and its ally Iran were blocking the ceasefire deal's implementation, as Iran allegedly imposed new conditions. A source close to the regime told AFP the government objected to the number of people in need of evacuation and wanted a list of their names.

Earlier on Wednesday, Turkish Foreign Minister Mevlut Cavusoglu also accused President Bashar al-Assad's government of blocking the deal brokered by Ankara and Moscow.

"We now see that the regime and some separate groups are trying to prevent this (agreement)," Cavusoglu told reporters in Ankara. "The evacuation could not take place in the full sense."

Pro-government forces trapped tens of thousands of civilians and rebel gunmen in eastern Aleppo after weeks of a crushing offensive operation to retake areas held by the opposition since 2012. 

Evacuations, due to start early Wednesday morning, were delayed as civilians waited in the cold with no sign of movement.

rs/msh  (AP, AFP, dpa, Reuters)