At least 12 civilians were killed Tuesday in "intensive" airstrikes carried out on the rebel-held eastern part of Aleppo, a group monitoring the Syrian conflict said.
"The dead included four children ... in the most intensive airstrikes undertaken by Russian planes since the regime announced on October 5 that they were decreasing their raids on areas in eastern Aleppo," Rami Abdel Rahman, head of the Britain-based Syrian Observatory for Human Rights told dpa.
"In the past few days there were raids; but they targeted areas where mainly fighting was taking place between the rebels and the regime forces, not neighbourhoods inside Aleppo," he said.
There have been conflicting reports about the number of casualties.
Activist Mahmoud Raslan, who is based in eastern Aleppo, said that Russian bombs had hit a building in Bustan al-Qasr that led to its collapse, killing eight people and wounding 20 others.
Ibrahim al Hajj, press officer at the White Helmet civil defence group in eastern Aleppo, said that "since this morning dozens of strikes were carried out."
"According to our records, 40 people were killed in Bustan al-Qasr, Ferdous and al-Katarigi neighborhoods," he said.
Aleppo, Syria's pre-war commercial hub, has been divided between Syrian President Bashar al-Assad's forces in the west and rebels to the east since fighting erupted for control of the city in mid-2012.
Russia intervened in Syria a year ago to prop up al-Assad's crumbling army.
Its air campaign has allowed government forces to reclaim some territory from both rebels and the Islamic State extremist group, most notably imposing a siege on eastern Aleppo where some 250,000 to 300,000 civilians are now thought to be trapped.