Kabul, Afghanistan ? Militants attacked a U.S. patrol with rocket-propelled grenades, killing three Americans in Afghanistan’s wild northeast, an official said Saturday.

U.S. troops used artillery to repel the attack in Nuristan province Friday, said Col. Tom Collins.

The clash in Nuristan province’s Waygal district on Friday also wounded three U.S. soldiers and one civilian as American forces kept up their hunt for Taliban fighters and extremists close to Osama bin Laden’s al-Qaida network that are holed up in remote mountains hugging the Pakistani border.

“We mourn their loss but their work continues,” Collins said, referring to the three slain soldiers. “We will honor them by continuing our mission to pursue extremists wherever they are.” He did not say whether the militants suffered any casualties.

In recent weeks, U.S. forces have been pushing to their northernmost points along the mountainous Afghan-Pakistan border, including Nuristan, opening military bases in one of the wildest regions in the country.

Their mission is to crush militants loyal to the Hezb-e-Islami militant group of renegade Afghan warlord Gulbuddin Hekmatyar, the toppled Taliban regime and remnants of bin Laden’s al-Qaida network.

Elsewhere, a British soldier in the NATO-led force was killed in a vehicle accident in the southern Helmand province on Saturday, a British Defense Ministry spokesman said.

The death brought to 19 the number of British forces killed since they deployed to Afghan-istan in November 2001. More than 3,000 NATO-led British troops are hunting Taliban fighters throughout Helmand, one of Afghanistan’s most violent provinces.

NATO took command of southern Afghanistan from the U.S. on July 31. The U.S.-led coalition is now focusing its attention on eastern Afghan-istan, where al-Qaida and Taliban are also active.