Kabul - Afghan officials said Tuesday that NATO forces shot dead four Afghan school students, but NATO said those killed were Taliban militants and their associates.

The incident happened around three kilometres south of Khost city, the capital of the south-eastern province of Khost, on Monday night, Mubarez Mohammad Zadran, a spokesman for the provincial governor, told the German Press Agency dpa.

He said all the deceased were civilians who were driving in a vehicle that failed to stop at military checkpoint. 'We condemn the attack,' he said.

The Education Ministry said in a statement that the four dead were students, aged 11 to 17. The ministry condemned the attack.

However, NATO said in a statement that two of the dead people were 'known insurgents' and the other two were their associates.

Afghan mourners gather to pray by the flower-decorated coffins of four children in Khost province on April 20, 2010. Four students were killed April 19 in crossfire between foreign soldiers and insurgents in eastern Afghanistan, the education ministry said. (Photo: Getty Images)

A vehicle approached a military convoy and did not stop despite warning shots, it said, adding, 'Several rounds were fired in an attempt to disable the vehicle, and finally shots were fired into the vehicle itself.'

'All four died of wounds at the scene,' it said.

Civilian casualties at the hands of international troops have become a delicate issue in Afghanistan. Such deaths have become the main source of tension between the Afghan government and foreign troops.

'We have a simple objective when it comes to civilian casualties,' Mark Sedwill, the senior NATO civilian representative in Afghanistan, said at a press conference on Tuesday in Kabul. 'And that is one civilian casualty is one too many. We will make all efforts to avoid them.'

Separately, a bomb strapped to a bicycle was detonated in the centre of Khost city close to the main police headquarters on Tuesday, causing no death or damage, Zadran said.

Meanwhile, unknown gunmen shot dead a deputy mayor in the southern province of Kandahar in what the Interior Ministry on Tuesday called a 'terrorist attack.'

Azizullah Zeyarmal was en route Monday night to a mosque in the provincial capital, also called Kandahar, when unknown gunmen opened fire on him, the ministry said in statement.

Zeyarmal died on his way to hospital, Mohammad Shah Farouqi, deputy provincial police chief, said.

No group took responsibility for the attack. However, the ministry said the attack was carried out 'by enemies of Afghanistan,' a term often used by Afghan officials to describe Taliban militants.

The shooting came hours after three children were killed and four other people were injured when a bomb hidden in a donkey-drawn cart exploded in front of the residence of influential tribal chief Haji Fazelluddin in the centre of Kandahar city.

Fazelluddin, a former district governor for Spin Boldak, was unhurt in the attack, but three of his nephews were killed.

On Thursday, a suicide bomber carried out an attack in the centre of Kandahar city, killing three Afghans and wounding around two dozen people, including foreign contractors.

Attacks that bear the hallmark of Taliban militants are on the rise in Kandahar, the spiritual home and birthplace of the Taliban, ahead of a much-publicized military operation in the province in the coming months.

Afghan and NATO officials have said their offensive was under way in the province, but it is to get a push in summer when thousands of additional US troops arrive in the region.

The total number of foreign troops in Afghanistan is set to rise to 150,000 from more than 125,000 currently stationed in the war-torn country.

Afghans carry bodies of four people killed when they ignored warnings to stop by one of NATO's convoys in Khost province late Monday, southeast of Kabul, Afghanistan, Tuesday, April 20, 2010. NATO said two of those killed in the incident were later identified as "known insurgents," although the provincial chief of police said the dead were all civilians, and included a 12-year-old child. (Photo: AP)