Updated

A Pakistani government official says a roadside bomb has struck in a school van with children and teachers in the country's northwestern tribal region, killing five people.

A local government administrator, Asmatullah Wazir, says the bomb went off on Tuesday in Khar, the main town in the Bajur tribal region. It killed two children, two female teachers and the driver.

Wazir says the van was badly damaged. It's unclear if there were any survivors.

No group immediately claimed responsibility for the attack. The Bjur region has been the scene of several military offensives against the Pakistani Taliban and foreign militants in recent years.

The attack comes against the backdrop of a major opposition rally underway since the weekend in the capital, Islamabad, which is demanding that the government step down.