Authorities said Wednesday the blast hit the policemen's car in Rubat-i-Sangin district of Herat province.
Officials in western Afghanistan say a roadside bomb has killed at least four Afghan policemen in the latest attack against the country's police force.
Authorities said Wednesday the blast hit the policemen's car in Rubat-i-Sangin district of Herat province. No one has claimed responsibility for the attack, but roadside bombs are frequently used by the Taliban to target police and security forces.
Meanwhile, NATO said Afghan and international forces detained two Taliban commanders and one other suspected militant in Wardek province. International forces say the commanders were responsible for several bombings and other attacks in the area.
NATO also said a bomb in southern Afghanistan Tuesday killed a soldier from Estonia.
The British defense ministry said a separate bomb attack killed two British soldiers and two Afghan soldiers on patrol in Helmand province Tuesday. Earlier in the day, a U.S. soldier was killed in a bomb blast elsewhere in the region.
This year has been the deadliest for U.S. troops in Afghanistan since international forces toppled the Taliban in 2001.
A suicide car bomber also struck Kabul's heavily secured main diplomatic and residential district Tuesday, killing at least eight people and wounding 40 others.
Authorities say the attack in the upscale neighborhood of Wazir Akbar Khan appeared to target former Vice President Ahmad Zia Massoud.
Massoud is the brother of Taliban opponent and famed guerrilla fighter Ahmad Shah Massoud, who was killed by al-Qaida two days before the September 11, 2001, attacks on the United States.
The former vice president survived Tuesday's blast, but two of his bodyguards were killed.
Some information for this report was provided by AFP.