BEIRUT, Lebanon - Government forces widened a bombing campaign in rebel-held areas of northern Syria on Monday, striking the northern city of Aleppo and a town on the Turkish border in raids that left an estimated 45 people dead, activists said.

The attack on the border town of Azaz was the latest attack using powerful but inaccurate "barrel bombs" on the Aleppo region, said an activist who goes by the name of Abu al-Hassan Marea.

He said residents in the town told him that 15 people were killed in the strike. Another activist group, the Local Coordination Committees, gave the same death toll.

The Azaz attack suggests the government is expanding its range of targets a week after it began an unusually heavy air offensive against Aleppo on Dec. 15, dropping barrel bombs on rebel-held areas from helicopters. Aleppo, Syria's largest city, is divided into government-and-rebel-ruled areas.

The Britain-based Syrian Observatory for Human Rights reported that multiple air raids on the Aleppo neighborhoods of Sukkari, Maadi, Marjeh, and Nairab left at least 30 people, including 12 children, dead Monday.

The death toll could rise as many people were seriously wounded. On Sunday, 65 were killed near an Aleppo marketplace in one of the bloodiest days of the air campaign, according to activists.