At least 32 civilians, including five children, were killed Thursday in Syrian regime air strikes and artillery bombardment on rebel-held areas in eastern Aleppo, a monitor said citing a new toll.

The Syrian Observatory for Human Rights said Thursday's toll, up from an earlier figure of 16 killed, was one of the heaviest since the regime launched an offensive on eastern Aleppo on November 15.

"There was an escalation in the evening, with successive bombardments," Observatory head Rami Abdel Rahman told AFP, adding that many people were trapped under rubble.