Nato said on Wednesday that it was revising its earlier claims that two unarmed Afghans killed by alliance troops were insurgents.
Nato had earlier identified as insurgents, two of the four men who were killed on Monday night after troops fired on a vehicle that approached their convoy. President Hamid Karzai and the victims' relatives immediately denied that and said they were all civilians.
On Wednesday, Nato said it should not have used the term 'insurgents' to describe the two. The organisation apologised for the deaths
of four people who were shot by international troops earlier this week, saying reports that two of them were insurgents were incorrect.
Four Afghan civilians were shot by foreign troops in Khost province on Monday, according to earlier reports from Nato's International Security Assistance Force (ISAF).
ISAF said on Tuesday a convoy returning to base was approached by a vehicle that turned off its lights and accelerated towards them. "ISAF personnel then fired warning shots, but the vehicle continued to accelerate. Several rounds were fired in an attempt to disable the vehicle, and finally shots were fired into the vehicle itself," it said in a statement. "All four died of wounds at the scene," it said of the occupants.
A spokesman for the Afghan education ministry, Mohammad Asif Nang, said the four were students and had died when "the foreign forces opened fire on them". A relative told AFP that the four students -- aged between 12 and 19 and including two brothers -- had been unarmed.
The initial claim was made because fingerprints taken from the two matched those found in a military biometric database. But their presence in the database does not necessarily mean they were insurgents.
It added that the presence of their fingerprints in the database "has not yet been determined to be relevant to the incident Monday night," ISAF said. "We sincerely regret this tragic loss of life," it quoted Major General Mike Regner, deputy chief of staff for joint operations, as saying.
Civilian deaths in Afghanistan's ongoing conflict are an incendiary issue, and though most are caused by Taliban-linked insurgents, they are generally blamed on the presence of foreign troops.
Nato and the United States have 126,000 troops fighting the Taliban-led insurgency, with the number set to peak at 150,000 by August. The United Nations said in a report earlier this year that most civilian fatalities -- 2,412 in 2009 and 2,118 in 2008 -- were caused by Taliban attacks.
Civilian deaths caused by Western troops fell 28 percent last year compared with the year before, thanks to measures taken to protect civilians, it added.
The deaths of four civilians earlier this month when US soldiers fired on a bus sparked furious protests in Kandahar and expressions of regret from Nato and US Defence Secretary Robert Gates.