KABUL, Afghanistan — A man wearing an Afghan security force uniform opened fire Wednesday inside a base in southern Afghanistan, killing two U.S. soldiers in what appeared to be the latest so-called "insider attack" to target foreign troops or contractors in the country.
NATO said two men in Afghan uniforms were shot in return fire and wounded, correcting an earlier NATO statement that had said two gunmen attacked the soldiers before being shot dead.
NATO said the gunman opened fire on a vehicle carrying international troops inside the base in Helmand province. Afghan authorities believe the shooting took place during an altercation.
A Pentagon spokesman, Navy Capt. Jeff Davis, said the two coalition members killed in the attack were Americans. He would not identify their service branch.
NATO did not identify the nationalities of those killed, nor the base on which the attack took place.
Karim Atal, the head of Helmand's provincial council, said the shooting happened on the Shorabak military base, which was formerly the British military's Camp Bastion, and the U.S. Marines' Camp Leatherneck.
"First, there was an argument between an army officer and the foreign soldiers, and it ended in shooting," Atal said.
No group claimed responsibility for the assault.
Taliban insurgents have been known to wear Afghan police or military uniforms to stage attacks on international troops. Others have opened fire apparently on their own accord, like an Afghan soldier who last year killed Maj. Gen. Harold J. Greene, the highest-ranked U.S. officer to be slain in combat since 1970 in the Vietnam War.
The shooting is the third "insider attack" on foreign forces this year. In January, three American civilian contractors were shot dead at Kabul airport by an Afghan soldier who was also killed. In April, an American soldier was killed by an Afghan soldier inside the governor's compound in eastern Nangarhar province.
Elsewhere on Wednesday, Taliban insurgents overran the Musa Qala district in Helmand, said Mohammad Sharif, the district's administrative chief. He said Afghan security forces had been resisting the Taliban attack for more than a week.
"We tried hard in the past days to fight the Taliban, but we didn't get any support from the government and finally we lost control of the district," Sharif said.
He said there were casualties among the Afghan security forces, though he couldn't provide a death toll.
The U.S. embassy in Kabul meanwhile warned on its website of a planned militant attack "against an unknown U.S. citizen" in Helmand's capital, Lashkar Gah, in "late August."
It said the attack would take place at the Bos Hotel, and that it had no further information.
Associated Press writers Mirwais Khan in Kandahar, Afghanistan, Robert Burns in Washington and Lynne O'Donnell in Kabul, Afghanistan, contributed to this report.