At least 12 people were said to have been killed by air strikes in Syria's northern province of Aleppo, a monitor group reported on Tuesday.Warplanes, believed to be Russians, carried out an air strike on the Islamic State (IS)-held town of Maskaneh in the eastern countryside of Aleppo on Tuesday, targeting a marketplace, according to the Syrian Observatory for Human Rights, Xinhua reported.The number of deaths is expected to rise due to the high number of critically wounded people, the Britain-based watchdog group added.Other activists placed the death toll in Maskaneh at 30.Opposition activists often accuse the Russian air force, which has been striking IS positions for over two months, of targeting civilian areas, a claim totally denied by Moscow.Meanwhile, the Observatory said clashes continued on Tuesday in the southern countryside of Aleppo, where the army backed by the Russian air strikes have been trying to advance against an array of jihadi groups.