BEIRUT — Airstrikes on a rebel-held city in Syria early Tuesday killed at least 15 people, wounded dozens more and demolished several buildings in one of the deadliest attacks since a cease-fire went into effect last year, Syrian activists and medics said.

The airstrikes hit the city of Idlib, the capital of a northwestern province of the same name that is almost entirely controlled by Syrian rebels and al-Qaida-linked insurgents.

The Britain-based Syrian Observatory for Human Rights said 26 people were killed, including 10 civilians – mostly women. The opposition-run Civil Defense in Idlib says 15 bodies were pulled from the rubble and that 30 people were taken for medical treatment. Conflicting casualty tolls are common in the chaotic aftermath of such attacks.

Opposition activists also reported airstrikes on several suburbs of the capital, Damascus.

The government and the opposition have repeatedly traded accusations of violating the cease-fire, which was brokered by Russia and Turkey and went into effect in December, shortly after the government recaptured the northern city of Aleppo.

The Observatory said it was not clear if the airstrikes were carried out by Syrian, Russian or the U.S.-led coalition that has been targeting the Islamic State group and al-Qaida’s affiliate in Syria. The Russian military denied that its warplanes have attacked Idlib.