The UN has called on the Taleban and opposition forces in Afghanistan to stop recruiting child soldiers to fight in the long-running civil war.

At a news conference in the Pakistani capital, Islamabad, the UN said it believed children as young as 14 were involved in the fighting in Afghanistan.

The UN said some were being sent straight to the frontlines.

Louis Georges Arsenault, the UN Children's Fund (Unicef) representative for Afghanistan, said: "We know it's increasing and that's why we are worried.

"There are more fighters being recruited and there are more students under the age of 18.

"That's why we are making it an issue much more now."

Although this is not a new problem, the UN stressed it was particularly concerned at the moment following a massive recruitment drive by the Taleban in the religious schools in neighbouring Pakistan.

It said thousands of students, including many teenagers, had joined the Taleban ranks in recent weeks to take part in the current offensive north of the Afghan capital, Kabul.

It is widely believed that many of the young students in the religious schools in Pakistan receive military training as part of the standard curriculum.

They are therefore keen to join the jihad, or holy war, in Afghanistan.