The U.S. military says it is working with Afghan officials to investigate clashes last week that may have led to the deaths of three civilians.

A military statement Tuesday says there are unconfirmed reports that two men and one woman were killed last Wednesday in an exchange of fire between coalition forces and unidentified attackers in the southern Uruzgan province.

The military says coalition forces on patrol that night returned fire after being ambushed with small-arms, machine-gun and rocket-propelled grenade fire in Deh Rawood district.

Coalition spokesman Col. Jerry O'Hara said the U.S. military regrets any loss of innocent life and offers condolences to the victims' families.

The military says it will discuss the incident with local tribal elders Tuesday.

Civilian deaths at the hands of international troops have caused tension between the Afghan government and western governments.

Afghan President Hamid Karzai has repeatedly called on international forces to do all they can to prevent civilian casualties during military operations.

In a separate incident in Uruzgan, the U.S. military says at least two insurgents were killed when the roadside bomb they were implanting exploded.

Elsewhere in southern Afghanistan, Taliban fighters killed two Afghan police officers in an attack Monday in Helmand province. One of the attackers also died.

Also Monday, the British Defense Ministry said one of its soldiers was killed by enemy fire in Helmand's Gereshk district.

British Prime Minister Gordon Brown had announced earlier that Britain has sent an additional 300 troops to southern Afghanistan in preparation for next year's presidential election.

Some information for this report was provided by AP and Reuters.