Afghan officials say at least 20 passengers in a minibus were killed after their vehicle struck a roadside bomb in the western province of Herat early Thursday.

Officials say women and children are among the victims. The attack wounded at least 12 other civilians.

An Afghan spokesperson says a similar improvised explosive device in the same district seriously wounded four people on Thursday morning.

Separately, Afghan officials say a truck bomb killed two Afghan security guards and wounded several others outside a U.S.-run provincial reconstruction team base in the eastern province of Paktia.

Police say a suicide truck bomber approached the heavily fortified entrance of the base and detonated his explosives after being confronted by Afghan security guards.

The Taliban claimed responsibility, saying a 70-year-old militant carried out the attack.

Meanwhile, local officials in Afghanistan's southern Kandahar province say a shootout between Afghan army and police officers Wednesday evening left three officers dead and at least five civilians wounded in the crossfire. Afghan officials say they are investigating the cause of the fight.

Violence in Afghanistan is at its worst since the U.S.-led invasion in late 2001, with international troop and Afghan civilian deaths reaching record levels.