A bomb has exploded in southwest Pakistan, killing at least three Pakistani soldiers and wounding six others.

Officials say the blast Wednesday in Quetta hit an army vehicle escorting school children, and that the death toll could rise.

There was no immediate claim of responsibility for the attack.

Quetta is the provincial capital of Baluchistan province. The area has been the scene of sectarian violence, militant attacks and unrest linked to a low-level insurgency.