NATO airstrike kills four Afghan soldiers

NATO has promised a full investigation into an airstrike on an Afghan army post that managed to kill four Afghan soldiers.

A joint US-Afghan force called in an airstrike on what turned out to be an Afghan army post after taking fire from there before dawn on Saturday, killing four Afghan soldiers and prompting an angry demand for punishment from the country's defence ministry.

Both NATO and Afghan authorities described the clash around a snow-covered outpost in Wardak province southwest of Kabul as a case of mistaken identity. NATO called the attack "unfortunate" and promised a full investigation.

The deadly strike threatens to strain relations between NATO and the Afghan government at a time when both sides are calling for a closer partnership in the fight against the Taliban. The fighting came on the heels of several recent cases of bloodshed between Afghans and Americans.

Interpreter kills two US soldiers

NATO and Afghan officials said an Afghan interpreter angry over "job issues" shot and killed two US soldiers on Friday before he was gunned down by an American service member in the same district as the airstrike. NATO officials said the two attacks appeared unrelated.

Saturday's fighting erupted about 3am when a group of US Special Forces and Afghan commandos approached a remote Afghan army outpost that was set up about 18 months ago to guard the main highway between Kabul and Kandahar.

NATO said the Afghan soldiers believed the unit was the Taliban and started shooting.

Seven Afghans wounded at checkpoint

The joint force returned fire and called in the airstrike, which killed the four Afghan soldiers, NATO and the Afghan Defence Ministry said. Seven Afghan soldiers at the checkpoint were wounded, provincial spokesman Shahidullah Shahid said.

Associated Press Television News video of the aftermath showed snow around the fortified compound blackened by the airstrike. American armoured vehicles stood guard on the highway about a kilometre from the hilltop outpost, while a US Black Hawk helicopter roamed the skies overhead.

"I am from this area, and I witnessed the entire incident myself," said local resident Khan Mohammed. "Planes arrived and bombed the Afghan National Army checkpoint. They hit some of the houses around the area with mortars."

Last year, the top US and NATO commander, Gen Stanley McChrystal, curbed the use of airpower to assuage rising public

anger over civilian casualties. Commanders still have the option of calling in airstrikes if they come under fire and civilians are not at risk.

Saturday's clash and the string of recent deadly encounters between Americans and Afghans are likely to stoke public anger against foreign forces - even though the United Nations reported this month that most civilian casualties were caused by the Taliban.

NATO said its troops opened fire on Friday on a taxi as it sped toward a patrol in Ghazni province, killing two civilians and wounding another. US soldiers shot and killed an Afghan imam on Thursday when his car approached a convoy on the eastern outskirts of Kabul.