Militants who took up to 250 Pakistani school children hostage in a northwestern town on Monday began freeing them after security forces surrounding the school withdrew, a government spokesman said.

The school children and teachers were seized in the town of Bannu following a gunfire clash with local police, officials said.

“About seven terrorists took the school children hostage. There about 200 to 250 children,” Hamid Nawaz, interior minister, told Agence France-Presse.

Violence has spread across Pakistan in recent months, seeping out of remote tribal regions that are sanctuaries for al Qaeda and Taliban militants and into cities and towns, raising fears about the stability of the nuclear-armed US ally.

Separately, a US diplomat was on Monday found dead in his Islamabad home, Mr Nawaz said.

Pakistani authorities, who were investigating the cause of this death, said they suspected that Keith Ryan had committed suicide.

In a brief statement, the US embassy said there would be a full investigation. “However, there does not appear to have been any foul play.”