A roadside bomb killed four Afghan policemen when it ripped through their patrol vehicle in western Afghanistan, a provincial government official says.
There was no immediate claim of responsibility, but roadside bombs are regularly planted by Taliban insurgents fighting a decade-long war against NATO-led foreign troops and Afghan government forces.
Afghan security forces are particular targets of the Taliban, as they prepare to take over full responsibility for security from 130,000 foreign troops by 2014.
But roadside bombs often kill civilians, with two consecutive bombings in the southern Afghan province of Helmand killing eight people on Thursday, including seven members of one family.
Over 3,000 civilians were killed in the war in Afghanistan last year, the fifth consecutive year the number has risen, the majority of them victims of roadside bombs, according to UN figures.