BEIRUT: Syrian warplanes struck targets in a rebel-held district in the contested northern city of Aleppo Friday, killing at least 15 people, wounding dozens of others and leaving some buried under the rubble of buildings, activists said.

The Britain-based, opposition-aligned Syrian Observatory for Human Rights and the Aleppo Media center said the airstrike targeted three buildings that were almost completely flattened in the rebel-held district of Kalassa, killing at least four children. They said many people were missing and residents were struggling to save people trapped under concrete blocks and debris.

The Observatory, which relies on a network of activists on the ground in Syria, said the death toll was likely to rise because many of the wounded were in critical condition and others were missing.

The Aleppo Media Center, which tracks violence in the city, said 33 people were killed and over a hundred wounded in the airstrike. The different figures could not be reconciled.

Director of the Observatory, Rami Abdul Rahman said his group had documented 15 people killed by name, adding that they were all civilians.

“It’s possible there were rebels, or Nusra Front or members of the Islamic State of Iraq and [Greater] Syria in the area, but so far, none of the people killed that we have documented were fighters, they were all civilian,” he told The Daily Star by telephone.

All the buildings were residential, he added.

Aleppo has been the focus of a violent struggle for control since rebel forces pushed in and began fighting with government troops there last summer. Since then, the battle has fallen into a stalemate, with districts carved up into rebel and government-held neighborhoods separated by checkpoints.

Activists also reported heavy fighting in several areas of the country, including the contested Qaboun district on the edge of the capital Damascus. Government troops have been trying to dislodge rebels from the area, which they use to lob mortars into the city.

Government forces also shelled the rebel-held village of Salma, in the province of Latakia, after Sunni rebels stormed a number of loyal Alawite villages in the province last week.