In what may be the worst "friendly fire" incident of the U.S. war in Afghanistan since it began in 2001, reports on Monday indicate that at least ten Afghan soldiers were killed and others wounded after their compound was fired on by U.S. military helicopters.

According to initial reports citing Afghan officials, a pair of U.S. gunships attacked the outpost in Logar Province in the morning hours. Pentagon officials have confirmed there was an "incident" in the area which is now under investigation.

Agence France-Presse reports:

The early morning raid in Baraki Barak district of Logar province comes as coalition forces increase air strikes on potential militant targets despite a drawdown of NATO forces after 13 years of war.

The bombing marked the second such incident in the area since last December when a NATO air strike killed five civilians and wounded six others.

"At 6am (0130 GMT) today, two US helicopters attacked a checkpoint in Baraki Barak," district governor Mohammad Rahim Amin told reporters. "The checkpoint caught fire ... and 10 Afghan army soldiers were killed," he added, revising down a previous estimate that 14 soldiers were killed.

A statement by Afghanistan's Ministry of Defense said that helicopters belonging to the U.S.-led military coalition had come under enemy attack in the area and returned fire, mistakenly hitting the army post.

Despite that statement, the Afghan army corps commander for the region, Sharif Yaftali, told the Washington Post that the U.S.-led coalition had "made a very big mistake" because the strike was during the daytime, and the outpost was perched on a hill top, making it visible for U.S. forces to determine that it was controlled by its allies.

"The Afghanistan flag was waving on our post, when we came under attack," said Yaftali.