Afghan and U.S. forces battled insurgents in central Wardak province Sunday, near the site where a U.S. army helicopter went down a day earlier, killing 30 U.S. troops, including special force Navy SEALs, eight Afghan commandos and an interpreter.

The fighting was ongoing as NATO teams tried to recover the wreckage of the twin rotor Chinook CH-47 transport helicopter from the remote Tagab Valley.

It was the worst loss of life suffered by U.S. forces in a single incident since the start of the Afghan war in late 2001.

NATO said Sunday it is investigating claims that Taliban insurgents shot down the aircraft. Local Afghan government forces said the helicopter was hit by a rocket following a U.S.-led raid on a Taliban compound. Eight Taliban fighters also were killed in the battle.

In other violence, NATO said four of its service members were killed Sunday in two separate insurgent attacks in southern and northeastern Afghanistan.

The French president's office in Paris says two French soldiers were among those killed and five others wounded in a clash in northeastern Kapisa province. There was no immediate confirmation of the nationalities of the other two troops.

The latest fatalities bring to 383 the number of coalition troops killed in Afghanistan so far this year.