BEIRUT - A Syria monitoring group and a rescue worker say an intense bombing campaign has targeted several neighborhoods in the rebel-held part of Aleppo city, including centers of the award-winning volunteer civil defense group known as the White Helmets.

The air campaign late last night and this morning comes as Syria's military command announced it is launching operations in Aleppo's rebel-held eastern quarters, raising concerns of imminent ground operations.

Rami Abdurrahman, of the Britain-based Syrian Observatory for Human Rights, says government troops seized buildings on the frontline, pushing back rebel fighters in the southern al-Amiriah district.

Ibrahim Alhaj, a member of the Syrian Civil Defense, confirmed the government troop movements. He says the bombing targeted two civil defense centers this morning in rebel-held Aleppo, putting one out of service.