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 exploded outside a U.S.-led military base in the eastern part of the country, killing two Afghan security guards and wounding several others.

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 has claimed responsibility for the attack, which happened at a U.S.-run provincial reconstruction team base in Gardez, the capital of the eastern province of Paktia.

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.