Fiercely independent tribesmen, angered by a U.S. air strike that killed 11 Pakistani soldiers this week, vowed to raise a militia to help Pakistan's army defend the border with Afghanistan.

Pakistan, a staunch ally in the U.S.-led war on terrorism, denounced Tuesday's attack on a border post in the Mohmand tribal region as "unprovoked and cowardly" and said it could undermine the cooperation in the battle against al Qaeda and the Taliban.

Elders from ethnic Pashtun tribes in Mohmand, one of seven semi-autonomous tribal regions, issued a statement late on Thursday condemning the attack as "naked aggression" and said they were ready to raise a "lashkar", or army.

"It's the duty of the government to protect and defend the frontiers and we are ready to raise a lashkar to help our army in their cause," the elders said.

"We are ready to fight for our homeland as we fought in Kashmir in 1948," they said, referring to the first war between Pakistan and India, a year after their partition.

Chanting slogans of "Down with America" and "Down with Bush", about 250 activists of an Islamic group paraded on the roads of Ghalanai, Mohmand's main town, to protest against the attack.

"We should wage jihad (Muslim holy war) to teach a lesson to America for this aggression," imam of the main mosque of Ghalanai, Abdul Khaliq, told the crowd.

The soldiers killed were manning a border post about 35 km (22 miles) northwest of Ghalanai.

U.S.-led ground forces from across the border in the eastern Afghan province of Kunar called for air support after coming under small-arms and rocket-propelled grenade (RPG) fire from militants occupying a ridge 200 metres (yards) inside Pakistan.

GRAINY IMAGES

A video released by U.S. authorities showed footage of the encounter shot by a reconnaissance drone aircraft, complete with a voice-over describing the incident.

The video was posted on the internet site here

The blurred, grainy images showed between five and seven figures scurrying among the rocks along the ridge, and flashes of gunfire and from RPGs, according to the American commentary.

In the final sequences, four precision bombs were shown exploding, but the commentator asserted that no military structure or posts were in the impact areas.

The U.S. military said the operation was coordinated with Pakistan and the Pentagon defended U.S. forces, saying initial indications pointed to a "legitimate strike" carried out in self-defence after they came under attack.

Pakistan contested the U.S. version and issued a protest.

On a visit to France, Pakistani Foreign Minister Shah Mehmood Qureshi said such "tragic incidents" only helped the militant cause and he called on the United States to cooperate much more with the Pakistani military.

U.S. Defense Secretary Robert Gates on Thursday said he regretted the death of Pakistani soldiers and praised Pakistan as an "incredibly important partner". He also invited Pakistani and Afghan officials to help investigate.

Pilotless drones have carried out several strikes targeting al Qaeda militants inside Pakistan's tribal areas.

The number of casualties suffered by Pakistani forces in Tuesday's attack was the worst they have suffered as a result of U.S. action in nearly eight years since the alliance was formed.

A new Pakistani government, led by the party of assassinated former prime minister Benazir Bhutto, has been negotiating with ethnic Pashtun tribes to get them to press the militants to give up a campaign of violence in Pakistan in which hundreds of people have been killed over the past year.

Gates told a news conference in Brussels on Friday the United States had been sceptical about such deals in the past but it was up to Pakistan to decide how to handle the situation.

"They are seeing if there's a way to negotiate arrangements with some of the tribes and I think we just have to give them some space to be able to pursue this," he said.