Moscow: Russia on Thursday said Syrian regime forces have begun pulling back from around a key road into the ravaged city of Aleppo, freeing up the way for aid deliveries.

“The Syrian armed forces are fulfilling their obligations and have started a gradual withdrawal of military hardware and all personnel from the Castello Road, which will allow for the unimpeded passage of humanitarian aid to the eastern part of Aleppo,” senior Russian officer Vladimir Savchenko said in a televised briefing.

The United Nations urged Syria’s government Thursday to allow immediate aid deliveries to hunger-stricken civilians after a fragile ceasefire was extended for 48 hours by Russia and the United States.

In a sign of renewed tensions between the two powers, who back opposing sides in the conflict, key regime ally Moscow accused Washington of failing to meet its obligations under the truce.

Savchenko said that rebel groups close to the crucial route did not appear to be carrying out a simultaneous pullback as agreed.

Washington said late Wednesday that US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov had spoken and agreed to prolong the ceasefire which began on Monday.

But hours later Russian military spokesman Igor Konashenkov slammed the US for what he called “rhetorical fog” intended “to hide the fact that it is not fulfilling its part of the obligations”.

“As of the third day (of the truce), only the Syrian army is observing the regime of silence. At the same time, the ‘moderate opposition’ led by the US is increasing the amount of attacks on residential districts,” Konashenkov said.

A ceasefire deal agreed by Washington and Moscow that went into force at sundown on Monday calls for the demilitarisation of the Castello Road, and Moscow had earlier said the Syrian army would start pulling back at 0600 GMT on Thursday.

The Syrian Observatory for Human Rights, a Britain-based monitor, said that government forces and rebel fighters remained on the road after that time and the army was not willing to pull back before opposition forces did so.

The truce deal has calmed much of the fighting in Syria but desperately needed humanitarian aid has not yet been allowed to reach civilian areas as planned under the agreement.

Twenty trucks loaded with aid for eastern Aleppo on Thursday crossed into a buffer zone between Turkey and Syria, high-level UN official Jan Egeland said.

UN Syria envoy Staffan de Mistura warned that the aid could not move into Syria’s second city before the Castello Road supply route had been fully secured.

Markets in east Aleppo have little to sell besides locally grown aubergines, parsley and other herbs.

“We were dying from shelling before, and now we’re going to starve to death,” said Abu Ebrahim, 53.

Russia - which is flying a bombing campaign in support of President Bashar Al Assad - insists that Syrian regime forces are fully respecting the truce, but US-backed rebels are violating it.

“The cessation of hostilities is not being fulfilled by the opposition units controlled by the US. Shelling continues, people are dying and houses are being destroyed,” senior commander Viktor Poznikhir said.

If the truce holds then Russia and the United States could start coordinating strikes against terrorists.

But Moscow insists that Washington is failing to get rebels to separate on the ground from radical terrorists.

Meanwhile, a member of the Syrian opposition’s High Negotiations Committee on Thursday denied there was any date for a resumption of peace talks with the government after Russia’s deputy foreign minister was quoted as saying they could happen at the end of September.

“We deny the existence of any such dates,” said George Sabra, adding that a resumption of talks was contingent upon developments on the ground in Syria, which he said now involved “nothing positive”.