UPDATE 2-Afghan police, U.S. troops kill three Taliban

(Updates with Taliban killed in Kandahar)

By Goran Tomasevic

SHAJOY, Afghanistan, March 22 (Reuters) - Afghan police backed by U.S. troops killed three Taliban fighters and captured three more in a 40-minute gun battle in southern Afghanistan on Saturday, a Reuters witness said.

The fire fight erupted after some 40 Afghan police officers, backed by a small team of U.S. mentors entered a village in the Shajoy district of Zabul province.

Taliban fighters fired on the troops before retreating to a nearby hill on motorcycles. The police and U.S. mentors chased the militants and surrounded them.

At the end of the battle, three Taliban were killed and three were captured, one of them wounded.

The United States is pressing its NATO allies to come up with more troops for Afghanistan at an alliance summit in Bucharest in early April. But all sides agree that building up the Afghan army and police is the key to long-term key stability.

The Afghan army is relatively well trained and equipped, but NATO has only filled 33 of 71 projected teams to bring the army from its current 50,000 troops to a target strength of 80,000.

The Afghan police has lagged far behind however. Officers are notoriously corrupt and often flee isolated outposts in the face of better armed Taliban militants.