Childhood innocence is soon lost in a country like Afghanistan. However, children have not only been the victims of the war but also its perpetrators - on both sides.

Youngsters are frequently used by the Taliban to carry out brutal attacks, according to the military and officials, with some apparently kidnapped or paid to join the war.

Afghanistan's National Directorate of Security says over 80 percent of the 112 would-be suicide bombers detained in the country in the past nine months were boys aged between 13 and 17.

But it is not only Taliban rebels who use children on the frontline - there are also teenagers in the Afghan police, although the government has just signed a pledge with the United Nations to stamp this out.

Among insurgents, the problem is on stark display in the Taliban's traditional stronghold of Kandahar Province, close to Pakistan's border region, where many Taliban leaders are thought to be based.

"In the firefight we have here, we can see the enemy. They're kids, like 15, 16 years old. And usually there's a 20-year-old who pays the kids," said US Army Captain Mike Cain of 1st Battalion, 66th Armored Regiment.

Cain, who is based near the city of Kandahar, added that the situation was "very hard for morale".

Another international military officer, based in Kabul and speaking on condition of anonymity, said that foreign troops had little choice but to kill those targeting them, regardless of their age.

"They are baby fighters. But what else can we do? They attack us and shoot at us with their AK47s and their RPGs (rocket propelled grenades) and if we don't kill them, they'll kill us," he added.

A UN report last year highlighted how children as young as 13 had been trained to carry out suicide attacks and plant explosives by the Taliban and other insurgent groups.

It quoted some children saying they had been kidnapped from their homes, while research from the non-governmental organization Action Aid in Kandahar has suggested that others are recruited while working on farms by militants offering them money.

Taliban spokesman Yosuf Ahmadi dismissed claims that the Taliban used child fighters when questioned about the issue by AFP.

"This is a mere claim made to divert the opinions of the public and the global community in order to create a dark and negative image of the Taliban," he said. "We strongly reject this claim and this is totally incorrect."

The Afghan government last month inked an accord with the UN to stop signing up youngsters into the armed forces.

Although Kabul officially bans the recruitment of under 18s, the armed forces are expanding rapidly - there has been a 36 percent increase in the last year to over 260,000 - putting pressure on them to sign up people fast.

This comes ahead of a planned transition of responsibility for Afghan security from international troops to their Afghan counterparts by 2014.

Another dimension of the problem is that Afghanistan has poor birth registration systems and little infrastructure for verifying age.