A suicide bomber has attacked the funeral of an anti-Taliban tribal elder in northwest Pakistan, killing at least 25 people.

Thursday's blast took place in the Lower Dir tribal area, as more than 100 people gathered in an open field for funeral prayers.

Police say the bomber targeted members of an anti-Taliban militia.

More than 60 people were wounded in the blast.

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.