Officials say bomb attacks have killed three American troops in Afghanistan, as NATO and Afghan forces killed 25 Taliban fighters in separate assaults, the AFP has reported.

The NATO-led International Security Assistant Force says two American troops were killed in an explosion on Friday. Another U.S. service member was killed the same day in a bombing in the south.

IEDs, home-made bombs planted on roadsides and difficult to detect, are claiming increasing numbers of foreign soldiers fighting the insurgency in Afghanistan.

In the deadliest incident reported Saturday, an airstrike killed 20 militants late Friday in Urgun district, said Hamidullah Zawak, spokesman for the provincial governor.

"These people intended to attack security posts and the U.S.-led coalition. They were killed before they could do so," he told AFP by telephone.

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The Associated Press contributed to this report.