A diplomatic solution appears unlikely as violence has escalated since a truce collapsed

Moscow on Monday slammed the United States and Britain for accusing Russia of "barbarism" and war crimes in Syria as Russian and Syrian warplanes continued to bomb rebel-held areas of Aleppo.

"We note the overall unacceptable tone and rhetoric of the representatives of the United Kingdom and the US, which can damage and harm our relations," Kremlin spokesman Dmitry Peskov told reporters.

A diplomatic solution to the fighting looked unlikely as US and Russian diplomats disagreed at a UN Security Council meeting called to discuss the violence, which has escalated since a cease-fire collapsed last week.

Moscow and Damascus were accused of war crimes at Sunday's emergency meeting of the UN Security Council.

"In short, it is difficult to deny, that Russia is partnering with the Syrian government to carry out war crimes," British Ambassador Matthew Rycroft said, adding that incendiary munitions "indiscriminate in their reach" were being used against Aleppo civilians.

US Ambassador Samantha Power meanwhile accused Moscow of "barbarism".

At least 124 people have been killed in the bombardment of rebel-held eastern Aleppo since the army on Thursday announced an operation to take the country's second city, said a monitoring group.

Russia's ambassador to the UN, Vitaly Churkin, on Sunday accused Washington of failing to convince armed opposition groups it supports to distance themselves from the al-Qaida-linked Nusra Front and abide by a short-lived cease-fire brokered earlier this month by Russia and the US.

Churkin however said that reviving the cease-fire was still a goal that Moscow could pursue if it was part of a "collective" effort on all sides.

Peskov said on Monday that the cease-fire has "little effect" but the Kremlin is not ready to bury it quite yet.

"Moscow is not losing the hope and political will to use maximum efforts to reach the point of political settlement," Peskov said on Monday.

Aleppo, divided since 2012 between government control in the west and rebel control in the east, saw some of its worst fighting in years last week.

UN Syria mediator Staffan de Mistura appealed to the Council meeting to come up with a way to enforce a cease-fire.

"I am still convinced that we can turn the course of events," he said, adding that he would not quit trying to bring peace in Syria.

China's UN envoy Liu Jieyi repeated a call for all sides to work harder to help find a political solution but also said counterterrorism was an "important component" to a resolution.

"The Syrian conflict has led to the rise and spread of terrorism. Without rooting out terrorism, there will be no peace for the Syrian people, and there will be no security for regional countries," Liu said.