NEW DELHI: At least eight Afghan soldiers have been killed and five others wounded in a US airstrike near Kabul, according to the governor of Logar province. If confirmed, the incident will be the deadliest case of “friendly fire” since the war began in 2001.

Logar governor, Mohammad Halim Fidai said that two helicopters struck an army outpost on a hill in Chiltan, district of Baraki Barak in Logar. The governor said that the helicopters were American. The US military confirmed that its troops had been involved in an incident in the area, without providing further details.

The Afghan Ministry of Defence said in a statement that Afghan soldiers had been killed and injured by coalition forces “whose helicopters, passing in the area, were fired at by the armed opposition”.

Col Brian Tribus, a US military spokesman in Afghanistan, said: “We are aware of an incident involving US forces in Logar province this morning. The incident is under investigation” (as quoted in The Guardian).

According to The Guardian, Fidai said that there was no fighting in Baraki Barak when the incident occurred on Monday. “There was no sign of the enemy,” Fidai said. “Normally, there is a potential enemy there in Baraki Barak, but these days, in general, the situation was very calm.”

The same article quotes the district governor of Baraki Barak, Mohammad Amin, blaming foreign troops for not coordinating with the local Afghan national army brigade. “There was [an Afghan] flag on the checkpoint, and the soldiers were in uniform, but they bombarded the checkpoint anyway,” he said.

An investigation team dispatched to the site came under fire, from what they say were Taliban forces.

Logar is an embattled province, with concerns regarding the resurgence of the Taliban as foreign troops begin to withdraw and other groups -- including a fledgling presence of the Islamic State -- begin to gain ground.

The US has however increased air strikes in the region, carrying out 106 attacks in June compared to 41 in May. The number of airstrikes are decreasing overall: Last year, the US carried out 2,363 air strikes compared to the end of June this year, when the number was 305.

Although it is rare for US forces to kill Afghan troops, this is not the first time such an incident has occurred. In March 2014, five Afghan soldiers were killed in a coalition airstrike in Logar’s district of Charkh. Three months later, five U.S. soldiers, an Afghan soldier and an interpreter in southern Zabul province were killed in a coalition airstrike as they were battling the Taliban.

Meanwhile, civilian casualties in Afghanistan reached a record high, with the UN Mission in Afghanistan concluding that the number of civilians killed or wounded in the troubled country climbed by 22 percent in 2014 to reach the highest level since 2009.

The UN agency documented 10,548 civilian casualties in 2014, the highest number of civilian deaths and injuries recorded in a single year since 2009. They include 3,699 civilian deaths, up 25 per cent from 2013 and 6,849 civilian injuries, up 21 per cent from 2013. Since 2009 -- when UNAMA began tracking casualties -- the armed conflict in Afghanistan has caused 47,745 civilian casualties with 17,774 Afghan civilians killed and 29,971 injured.