By Ellen Francis and Angus McDowall
BEIRUT (Reuters) - Syrian rebels and civilians showed no sign of leaving the besieged opposition-held sector of Aleppo on Friday, despite a Russian deadline to resume bombing Syria's largest city at nightfall after a 17-day pause.
The rebels' own shelling of residential parts of government-held western Aleppo has meanwhile killed dozens in the past week as insurgent groups staged a counter-attack from outside the city aimed at breaking the siege on areas they control.
The government sent ambulances and buses to bring people out of the besieged zone as it has done at other times during the pause, but there was still no sign that anybody would leave.
Residents contacted by Reuters seemed resigned to the resumption in bombing, which killed hundreds of people in late September and early October as the government and its Russian allies abandoned a ceasefire to launch their assault on the biggest urban area in opposition hands.
"Nothing can be done. Nobody can stop the planes," said Bebars Mishal, an official with the "white helmets" civil defense volunteer group in eastern Aleppo, which digs victims out of the rubble and runs an ambulance service.
He said there was no way for rescue workers or medical staff to prepare in advance of the expected resumption of attacks: "All we can do is take precautions and be ready 24 hours a day."
Moscow and Damascus say their pause in bombing the city will end at 7 pm (1600 GMT), accusing rebels of having used the pause to reinforce and launch attacks on government-held areas.
The government and its Russian allies say they target only militants, and that fighters are to blame for civilian casualties by operating in civilian areas.
Western countries say the bombing has deliberately targeted hospitals, aid workers and bakeries and Washington has accused Moscow of "war crimes". Rebels say the aim is to drive out civilians, some 275,000 of whom remain in the besieged zone.
"They call it a ceasefire. The regime hasn't let us hear the end of it," said Modar Shekho, a nurse in rebel-held eastern Aleppo. "As usual, when it ends they will let the bombardment loose. We've gotten used to this."
Syria's army, backed by Lebanese, Iranian, and Iraqi Shi'ite militias and Russia's air force, launched a major offensive to retake eastern Aleppo from rebel groups on Sept. 22 after a series of advances allowed them to besiege it this summer.
Aleppo has become the focal point of fighting in Syria's war, now in its sixth year, pitting President Bashar al-Assad and his allies against Sunni rebel groups including some supported by Turkey, Gulf Arab monarchies and the United States.
The city has been divided between the government-held western sector and rebel-held east for years. Winning full control of it would be the biggest victory so far for Assad's government in a war that has killed many hundreds of thousands of people and driven more than half of Syrians from their homes.
"NOBODY WILL LEAVE"
Damascus and Moscow declared a unilateral four-day pause in strikes on Oct. 18, promising rebels and residents safe passage to leave the city and have extended it for most days since, although some attacks have continued.
Russia, which has brought an additional aircraft carrier to Syria's coast, said on Wednesday that all rebels must leave Aleppo by Friday evening, adding its moratorium on air strikes could not be extended because of rebel shelling.
A witness in western Aleppo at Bustan al-Qasr, near a crossing point set up by the government to allow civilians to flee the rebel area, told Reuters on Friday he could see people waiting for relatives to come from the east. Buses and ambulances were waiting for them, but so far there was no sign of an exodus.
A woman at Bustan al-Qasr who was covering her face said she hoped the people in eastern Aleppo would be able to leave safely and peacefully.
Rebels have rejected the demand they withdraw.
"Nobody will leave and the Russians will escalate. The Russians declared this," said Zakaria Malahifji, a Turkey-based official from the politburo of the Fastaqim group, which is present in Aleppo.
The opposition says Damascus and its Russian and Iranian allies aim to win the war by depopulating rebel-held areas, starving the population out or bombing them into flight.
"The Russians are adopting a policy of demographic change with the regime and Iran, and their intentions are no longer hidden," an official from the Nour al-Din al-Zinki rebel group said.
In recent months other opposition-held areas have surrendered after long army sieges. The government calls the process reconciliation, offering safe passage out for rebel fighters who abandon territory and lay down their arms.
It has proposed a similar program to end the siege of eastern Aleppo, opening what the army calls safe corridors, and sending ambulances for injured civilians and green city buses to transport fighters to Idlib, a rebel-held area.
But so far only a very small number of people have left the rebel-held zone since late October. Damascus has accused rebels of stopping people from leaving, including by shelling the safe corridors, which rebels have denied.
"I wish civilians would exit ... but I expect that won't happen, not under these circumstances," Fadi Ismail, an official based in Aleppo in Syria's reconciliation ministry, told Reuters via telephone.
Ismail said prospects for a deal with rebels looked bleak. "There must be military action, of course," he said, if no one evacuated.
The United Nations has said it does not have security guarantees needed to deliver aid into eastern Aleppo. It opposes evacuations of civilians from besieged areas unless they are voluntary.
After their offensive began in late September, pro-government forces managed to take ground in northern Aleppo including a camp for Palestinian refugees and smaller areas in the south, but made fewer advances into densely populated areas.
Rebels launched a counter-attack a week ago against the western edge of government-held areas from the surrounding countryside. They have made progress in the Dahiyet al-Assad suburb and the 1070 apartment blocks district, using 15 suicide car bomb attacks during the week, a war monitor said.
The Britain-based Syrian Observatory for Human Rights said the rebels had killed 69 civilians including 25 children in shelling during their counter-attack.
(Additional reporting by Kinda Makieh in Damascus and Tom Miles in Geneva)