Rahim Faiez, Associated Press 12:40 p.m. EDT August 26, 2015

U.S. soldiers inspect the site of a suicide attack in the heart of Kabul, Afghanistan, Saturday, Aug. 22, 2015.(Photo: Massoud Hossaini, AP)

KABUL, Afghanistan (AP) — Two men wearing Afghan security force uniforms opened fire Wednesday inside a military base in southern Afghanistan, killing two U.S. soldiers before being shot dead themselves, officials said.

NATO offered few details about the shooting in Helmand province, which appeared to be the latest so-called “insider attack” to target foreign troops or contractors in the country. Afghan officials said authorities believe an argument sparked the shooting.

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.

In a statement, NATO said the two men in Afghan uniforms opened fire on a vehicle with international troops inside it. Both shooters were killed when NATO forces returned fire, it said.

NATO did not identify the nationalities of those killed, nor the base on which the attack took place. It said the attackers wore “Afghan National Defense and Security Forces uniforms,” which include the country’s police, military and border patrol.

Karim Atal, the head of Helmand’s provincial council, said the shooting happened on the Shorab military base, which was formerly the British military’s Camp Bastion.

“First, there was an argument between an army officer and the foreign soldiers, and it ended in shooting,” Atal said.

A police official in Helmand, who spoke on condition of anonymity as he wasn’t authorized to discuss the attack, also said an argument likely sparked the shooting.

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.

Meanwhile Wednesday, Taliban insurgents overran the Musa Qala district in Helmand province, 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.

Associated Press writers Mirwais Khan in Kandahar, Afghanistan, and Robert Burns in Washington contributed to this report.

Copyright 2015 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Read or Share this story: http://usat.ly/1EjbMNs