American troops opened fire after an “enemy insider” shot and killed an Afghan commander in central Afghanistan on Wednesday, officials said, in yet another deadly Taliban-claimed infiltration.

According to the Afghan defence ministry, Colonel Mateen Mujtaba, who headed the 3rd army division in Ghazni province, was conducting a security assessment in Qarabagh district when an Afghan soldier started shooting.

Mateen was “killed by an army soldier who was in fact an enemy insider,” the defence ministry said in a statement.“The attacker was also killed when soldiers returned fire.”

The Taliban claimed the attack, saying US soldiers had also been killed.

Resolute Support, the US-led NATO mission in Afghanistan, said no US or coalition troops had been killed or wounded, but declined to comment further.

According to Amanullah Kamrani, a member of the Ghazni provincial council, Mateen was boarding a helicopter after a meeting with US advisors when he was attacked.

“The attacker was killed when Americans returned fire,” Kamrani told AFP.

Insider attacks, sometimes referred to as “green on green,” are a constant threat in Afghanistan.

In October, powerful police chief General Abdul Raziq was among three people killed in a brazen insider attack on a high-level security meeting in Kandahar.

The meeting was also attended by General Scott Miller, the top US and NATO commander in Afghanistan.

He escaped unhurt, but US Brigadier General Jeffrey Smiley was among 13 people wounded in the shooting, which the Taliban said had targeted Miller and Raziq.

20 Afghan commandos ambushed

Meanwhile, at least 20 Afghan commandos were killed in a Taliban ambush in western Afghanistan, officials said on Wednesday, marking yet another loss for the elite troops amid a push to end the war.

Provincial governor Abdul Ghafoor Malikzai said the special forces soldiers were ambushed on Monday after flying into Abkamari district in Badghis province, a known Taliban hot spot.

“The commando forces descended... without coordination with other security forces,” Malikzai told AFP.“They were surrounded by Taliban fighters and fought for hours.

Unfortunately, 21 of them were killed. Some were captured,” he added.

The Afghan defence ministry had no immediate comment.

Abdul Aziz Bek, the head of the Badghis provincial council, put the toll at 29 killed, saying some of the Afghan soldiers had been slain after they'd been captured.

“Some 40 commando soldiers were brought in by four helicopters from neighbouring Ghor province for an operation, but they got ambushed as soon as they descended. Only 11 of them were rescued later,” Bek told AFP.

The Taliban claimed responsibility, saying over 30 soldiers had been killed.

Afghanistan's small, US-trained special operations forces represent only a small fraction of the approximately 300,000-member security forces.

The battle-hardened commandos have been carrying out most of the offensive operations being launched across the country, and have suffered high casualties.

The Afghan war grinds on even as the US and the Taliban have held talks about a possible peace agreement, with Afghan fighters and the Taliban still taking daily losses.

On Saturday, four Afghan security forces were killed in Qala-i-Naw, the capital of Badghis province, when Taliban insurgents attacked a hotel.