Pakistan officials say a bomb blast in the country's remote northwest has killed six people.

Authorities say the bomb that exploded Sunday was planted in a donkey cart in the market of Mastak town.

A local government official says the explosives were detonated with a remote-controlled device.

No group has claimed responsibility. Officials have blamed similar attacks in the past on the Taliban and Islamist militants.

In other news from Pakistan, 21 people were killed when a minivan and a bus collided Sunday in southern Sindh Province.

Pakistan has one of the world's worst records for deadly traffic accidents, blamed on poor roads, badly maintained vehicles and reckless driving.