At least 27 children and a female teacher were killed and more than three dozen people injured when the roof of a private school collapsed in northwestern Pakistan on Thursday, as rescuers searched through the debris for anyone still trapped.

Several children remained buried under the rubble in Peshawar, the capital of Khyber Pakhtunkhwa province, emergency services spokesman Bilal Faizi said.

Mohammad Asim, a hospital spokesman, confirmed the casualties, adding that some of the injured were in critical condition. All the children killed or injured were aged 13 or younger, he said.

The hospital declared an emergency as medical staff treated the wounded. Rescue workers continued removing debris to reach those believed to be trapped beneath the collapsed structure.

Witnesses said local residents were among the first to arrive at the school in a densely populated neighbourhood in central Peshawar. Rescue teams reached the scene within minutes of receiving the alert.

Resident Mohammad Khan said rescuers were carefully clearing the debris to reach children and school staff feared to be trapped underneath.

Outside the school and at the state-run Lady Reading Hospital, distressed parents waited for information about their children, uncertain whether they had survived.

The cause of the collapse was under investigation. Peshawar police chief Saeed Ahmed said the school owner had been arrested, adding that the building was structurally weak.

In July, four schoolchildren were killed when the roof of a tutoring centre under construction collapsed in Lahore.

Building collapses are common in Pakistan, where construction standards are often poorly enforced. Many buildings are constructed with substandard materials, while safety regulations are frequently ignored to cut costs.