AMMAN/BRUSSELS: Syrian rebels said on Tuesday they had repelled an army offensive in southern Aleppo as Russian and Syrian warplanes pounded residential areas, while nations spoke of rebuilding a peace process the United States broke off this week.

U.S. Secretary of State John Kerry, who announced on Monday that Washington was suspending talks with Moscow due to Russia’s role in the offensive, said peace efforts must carry on.

Turkey, long one of the main foes of Syrian President Bashar al-Assad but which has lately repaired its damaged ties with his ally Russia, said it planned to make a proposal to Washington and Moscow to resurrect a ceasefire that collapsed last month.

But on the ground there was no sign of peace with potentially the biggest and most decisive battle of the five-and-a-half year war unfolding as pro-government forces sought to drive anti-Assad rebels from their last major urban stronghold.

Assad’s government, with Russian air support and Iranian ground forces, launched the assault on Aleppo last month, a week into a ceasefire agreed by Washington and Moscow.

The United States and other Western countries say Moscow and Damascus are guilty of war crimes for deliberately targeting civilians, hospitals and aid deliveries to crush the will of more than 250,000 people trapped under siege in Aleppo. The Syrian and Russian governments say they target only militants.

Rebels said they inflicted losses on pro-government fighters after hours of clashes on the fringe of Sheikh Saed district, at the southern edge of the rebel-held eastern half of Aleppo city.

“We repelled their attempt to advance in Sheikh Saed and killed 10 regime fighters and destroyed several vehicles,” said a fighter from the Failaq al-Sham rebel group who gave his name as Abdullah al-Halabi.

Pro-government media said the Syrian army was pressing ahead in a major campaign supported by Iranian-backed militias and Russian air power to take full control of Syria’s largest city, divided between rebel and government zones since 2012.

In the 15 days since the collapse of the ceasefire, war monitor the Syrian Observatory for Human Rights said it had documented the deaths of 293 civilians in besieged east Aleppo as a result of air strikes and shelling, including 20 on Tuesday. It has documented 25 deaths in government-held west Aleppo from rebel shelling during the 15 days.

Opposition sources give higher death tolls in the besieged rebel-held sector, under attack from bombing described as unprecedented in its ferocity. Many hundreds of wounded people have been brought to a handful of functioning hospitals, which are short of supplies and have themselves come under attack.

Aid group Médecins Sans Frontières said four of the last eight functioning hospitals in eastern Aleppo had been damaged by air strikes in the past four days. “Doctors are performing brain and abdominal surgeries … on the floors of the emergency rooms, for lack of available operating theatres,” said Pablo Marco, MSF’s Middle East operations manager.