The death toll from a suicide attack on a funeral in northwest Pakistan has risen to 40.

Thursday's bombing targeted members of an anti-Taliban militia as they gathered for funeral prayers in the Lower Dir tribal area. Some 70 people were hospitalized with injuries.

No one has claimed responsibility for the attack, but the Pakistani Taliban has stepped up attacks on pro-government tribes.

On Tuesday, gunmen opened fire on a school bus on the outskirts of the city of Peshawar, killing four children and the driver.

The Taliban claimed responsibility for the shooting, saying the children were from a local tribe that has been fighting insurgents in the region.