Syrian and Russian military officials could not immediately be reached for comment on the latest air strikes.

The Civil Defence, a rescue service operating in rebel-held areas, said on its Twitter feed the air strikes had killed 25 people, 15 of them at a market place in the Fardous district.

Heavy aerial bombardment of eastern Aleppo resumed on Tuesday after a pause of several days which the Syrian army said was designed to allow civilians to leave.

President Bashar al-Assad, with military backing from Russia and Iranian-backed militias, aims to take back all of Aleppo, which was Syria's biggest city before the outbreak of war in 2011. The city has been divided between government and rebel control for years.

The Syrian Observatory for Human Rights, a Britain-based organisation that reports on the war, also reported heavy air strikes against the rebel-held Eastern Ghouta area near Damascus.

A Syrian military source said that warplanes had struck several locations to the south and southwest of Aleppo.

Western states have condemned the Syrian government and Russia over their latest onslaught against rebel-held Aleppo. The Syrian army has denied any targeting of civilians but France and the United States have called for an investigation into what they said amounted to war crimes by Syrian and Russian forces in the city.

Russia on Saturday vetoed a French-drafted United Nations Security Council resolution that would have demanded an immediate end to air strikes and military flights over Syria's Aleppo city.