By Angus McDowall and Tom Perry
BEIRUT (Reuters) - A senior Syrian opposition official accused Russia on Friday of procrastinating in talks with rebels over Aleppo, signaling no progress in diplomacy which rebels hoped would ease dire conditions in the city where they are in danger of defeat.
Buoyed by its rapid capture of several whole neighborhoods, the government on Friday took journalists on an escorted tour of the ruined northeast Aleppo districts which fell on Sunday and Monday, and which the army is sweeping for mines.
The rebels' talks with Russia, the most powerful ally of President Bashar al-Assad, in Ankara point to the bad set of options they face. The government assault aims to take Aleppo by the time U.S. President-elect Donald Trump takes office.
"There is severe procrastination by the Russians," the official said, speaking on condition of anonymity due to the secret nature of the talks. "There is absolutely no seriousness," he added. However, analysts have said rebels may have to agree to withdraw, depending on the terms.
Russian Foreign Minister Sergei Lavrov, speaking at a news conference in Rome, acknowledged contacts with the Syrian opposition and added that "a military solution to the Syria conflict does not exist".
The talks have been going for about two weeks and are the first between Russia and rebel groups who say they have been abandoned by the West.
Moscow's warplanes have played a critical role in helping to turn around Assad's fortunes from summer 2015, supporting the offensive against Aleppo by the Syrian army and its allies - Iran's Revolutionary Guards and Shi'ite militias from Lebanon and Iraq.
Some rebel groups are supported by the United States, Turkey and Gulf monarchies, but Syria's insurgents also include jihadist militants such as the former al Qaeda affiliate Jabhat Fateh al-Sham, previously known as the Nusra Front.
The front lines around the rebel-held sector of Aleppo have mostly held steady since Monday, when insurgents were forced from more than a third of the area they have controlled for several years in an assault by the Syrian army and its allies.
However, one Syria expert said that although the smaller area they occupied should make defending it easier for rebels, the cumulative impact of intense bombardment could force them to make a deal to withdraw, depending on the terms offered.
"The opposition's ability to defend itself under this offensive is very much in question, and it's easy to imagine that an eventual withdrawal seems increasingly likely," said Noah Bonsey of the International Crisis Group.
The army's advances have allowed it to reopen the northern section of the city's ring road, state TV reported, a move that may improve its transit and communications options near the new front line on another stretch of that highway near the airport.
A Syrian army officer escorting journalists on a tour of Aleppo's recaptured northeast said the army had to evict militants from all parts of the city. "This will happen soon," the officer told Reuters TV during the tour.
He said militants who had already given up their arms would benefit from an amnesty, but those who continued to fight "will have another fate".
Recently captured districts of Aleppo bore the marks of the recent fighting. Buildings in several districts had partly collapsed or been damaged by the bombardment. Burnt-out cars and buses had been used as a barricade.
Soldiers in dark green and brown camouflage uniforms carried their weapons as they walked, or rode on the back of trucks through the area. In one place, a vehicle loaded with missiles stood by the roadside.
In the south of their sector, rebels retook some positions from the army and its allies in the Sheikh Saeed district where fighting in past days has been concentrated, the Syrian Observatory for Human Rights, a British-based war monitor, said.
The rebels now control about 70 percent of Sheikh Saeed, located at the southern tip of the rebel-held area, the Observatory added. A Syrian military source had said on Wednesday that the army had fully recaptured Sheikh Saeed.
Rebel shelling of government-held areas in western Aleppo also killed several people on Friday, state television reported.
Aleppo has endured the fiercest fighting in Syria for months as Assad and the rebels trying to oust him struggle for control of a city that was the country's most populous before the war. Its fate is seen on both sides as pivotal to the wider course of the conflict.
The fighting has added to a humanitarian crisis in Aleppo, where the rebel-held eastern districts have been besieged since the summer under heavy bombardment, with hundreds dying from air strikes and shortages of food, medicine and fuel.
The United Nations said on Thursday it was very worried about the lack of adequate shelter for the tens of thousands displaced within the city by fighting as winter draws on.
Save the Children, an international charity, said some children had died after becoming separated from their parents in the chaos of the flight from front lines and then killed as they ventured into the open under bombardment or air strikes.
Turkey, a main supporter of the rebellion against Assad, on Friday accused him of being responsible for the deaths of 600,000 people in the conflict, which has raged since 2011, and called for an immediate cessation of hostilities.
(Additional reporting by Firas Makdesi in Aleppo, Ellen Francis in Beirut, Isla Binnie in Rome, Nick Tattersall in Istanbul and Tom Miles in Geneva; Writing by Angus McDowall)