A roadside bomb blast has killed at least 10 people near the troubled Swat Valley in northwestern Pakistan, local authorities say.

The bomb, apparently detonated via a remote control, exploded near a prison van and a school bus at Kwago Obbo in the Upper Dir district in North West Frontier Province killing three school children, four policemen and three prisoners, Press TV's Pakistan correspondent reported.

"The van was carrying prisoners to jail after they had left the court," a police officer said.

The injured were immediately taken to a nearby hospital for treatment.

Senior police official Khurshid Khan said the three children were killed as their school bus was driving past at the time of the blast.

Earlier on Thursday, another bomb exploded near heavy-guarded anti-terrorism squad (ATS) barracks in Pakistan's capital.

HSH/MMN