The strict Islamist group’s one-legged military commander, Mullah Dadullah, also denied NATO charges the guerrillas used villagers as human shields in combat against foreign forces.

The warning came as a a provincial official said a bomb had killed at least 14 civilians in the rugged southern province of Uruzgan on Friday.

‘We want to inform the foreign forces and their slaves that their defeat is inevitable in Afghanistan,’ Dadullah told Reuters by satellite phone from a secret location.

‘The Taleban’s mujahideen are ready to fight until death and in the coming days will increase their activities and suicide attacks to such an extent that the infidel forces will not get a chance to rest.

‘The Taleban will not let the the killers of Afghan women and children rest in peace and will continue to target them.’

Witnesses and officials say NATO air strikes in neighbouring Kandahar province, where the Taleban began and remain strong, killed at least 50 civilians this week in an area the alliance had said it had cleared of insurgents in an offensive last month.

 Taleban video

The Defence Ministry, NATO and a team of local elders appointed by President Hamid Karzai are investigating.

Fighting across Afghanistan, but mainly in the Taleban’s stronghold in the south, is the worst it has been since a U.S.-led invasion drove the group from power in 2001.

More than 3,000 people have died, mostly militants but including hundreds of civilians and more than 150 foreign soldiers.

Recent Taleban video obtained by Reuters shows a robust Dadullah trekking through the mountains of Uruzgan and firing a heavy machine gun.

The video also shows large numbers of well-armed and well-equipped Taleban fighters in combat and looting a remote police post. Insurgents are also seen beheading apparently dead ‘spies’ and suicide bombers vowing to drive out foreign infidels.

NATO’s German soldiers have sparked anger in Afghanistan after pictures apparently showing some of them playing with a human skull in the country were published in a German magazine and on television.

One photograph printed by the Bild newspaper on Wednesday showed an unidentified soldier, dressed in desert fatigues, clutching the skull next to his exposed penis.

Germany, with 3,000 troops in Afghanistan, has boosted security at its embassy in Kabul and missions across the Middle East in case of a backlash.

Some analysts say the scandal will undermine NATO’s image in the same way photos of US troops abusing prisoners in Iraq’s Abu Ghraib prison tarnished the United States operation there.

‘This act can be used as a catalyst for the Taleban to promote their profile and to increase the number of people who join them,’ Nadir Nadiry, a member of the independent human rights commission, said.

Germany has launched an investigation into the photos, taken in 2003 and 2004.