A bomb has exploded at a funeral in northwest Pakistan, killing at least 18 people.

Thursday's blast took place during funeral prayers for a tribal leader in the Lower Dir tribal area. More than 50 people were wounded in the attack.

Police say the bomb targeted members of a militia that had been formed by the tribal leader to oppose Islamic militants in the area.

Authorities were looking into whether a suicide bomber was responsible for the blast.

No one claimed responsibility for the attack.

The tribal region is close to the Afghan border and has seen violence between Islamist militants and Pakistani security forces.