Russia says a draft UN resolution for a truce in the Syrian city of Aleppo is unacceptable, as Moscow faces growing international pressure to stop a devastating bombardment of the city backed by Russian air power.
Russia's Deputy Foreign Minister Gennady Gatilov said on Friday that a draft put forward by France contained a number of unacceptable points and politicised the issue of humanitarian aid.
But Foreign Minister Sergei Lavrov said Russia would support an eye-catching proposal by UN Syria envoy Staffan de Mistura to escort militants out of Aleppo personally.
Russia was ready to call on the Syrian government to allow fighters from the Islamist Nusra Front to leave the city with their weapons, Lavrov said.
He was speaking a day after Syrian President Bashar al-Assad offered fighters and their families an amnesty to leave rebel-held eastern Aleppo under guarantee of safe passage to other parts of Syria held by the insurgents.
However, rebels have told Reuters they do not trust Assad, and have said they believe such an agreement would be aimed at purging Sunni Muslims from eastern Aleppo.
The offer follows two weeks of the heaviest bombardment of the five-and-a-half-year civil war, which has killed hundreds of people trapped inside Aleppo's eastern sector and torpedoed a US-backed peace initiative.
More than 250,000 people are believed to be trapped in eastern Aleppo, facing severe shortages of food and medicine.
German Chancellor Angela Merkel urged Russia to use its influence with the Syrian government to end the bombardment of Aleppo, as her government opened the door to possible sanctions against Russia for its role in the conflict.
Merkel said there was no basis in international law for bombing hospitals and Moscow should use its influence with Assad to end the bombing of civilians.
"Russia has a lot of influence on Assad. We must end these atrocious crimes," Merkel said.
US Secretary of State John Kerry said Russian and Syrian actions such as bombing hospitals in Syria cried out for a war crimes investigation.
"Last night, the (Syrian) regime attacked yet another hospital and 20 people were killed and 100 people were wounded. Russia, and the regime, owe the world more than an explanation about why they keep hitting hospitals and medical facilities and children and women," Kerry told reporters in Washington.
"These are acts that beg for an appropriate investigation of war crimes and those who commit these would and should be held accountable for these actions."
The UN Security Council was expected to vote on Saturday on a draft resolution that calls for an immediate truce in Aleppo, a no-fly zone and access for humanitarian aid.
Russia is expected to use its power of veto.
The Syrian army and its allies clashed on Friday in the south of Aleppo with rebels seeking to oust Assad, part of a pro-government offensive to retake the city.
Air strikes on rebel-held eastern Aleppo by the Syrian military and Russian jets remained significantly lighter than during the previous two weeks following an army announcement on Wednesday that it would lessen its bombardment.