The U.S.-led coalition in Afghanistan released footage Thursday of a skirmish with militants that Pakistan claims resulted in an airstrike on one of its border posts that killed 11 of its troops. Pakistan has lodged a strong diplomatic protest, saying the bombing of the Gorparai post in the Mohmand frontier region on Tuesday was a "completely unprovoked and cowardly act." But Pakistani and U.S. officials have given widely differing accounts of an event that threatens to further sour relations between key allies in Washington's war on terror.

To support its version, the coalition on Thursday took the unusual step of releasing excerpts of a video shot by a surveillance drone circling above the mountainous battle zone.

The grainy, monochrome images show about a half-dozen men firing small arms and rocket-propelled grenades from a ridge at coalition troops off-camera in the valley below.

According to the voiceover in the video, the ridge is in Afghanistan's Kunar province, about 200 yards from the Pakistan border and close to the Gorparai checkpoint.

Neither the checkpoint nor any other structures are visible in the video excerpts.

The voiceover says the coalition forces were on a reconnaissance mission and returned fire as they tried to break contact and move to a point where a helicopter could pluck them to safety.

The video shows the "anti-Afghan militants" moving to a position identified as inside Pakistan and the impact of a bomb which the voiceover says killed two of them.

The survivors then fled into a ravine, where three more bombs were dropped, nearly three hours after the clash began. The voiceover said all the militants were killed.

One of the bombs fell off screen, and U.S. officials said about a dozen bombs were dropped in all.

On Wednesday, U.S. diplomats offered apologies for the reported casualties. But the Pentagon insisted that the drone footage of the bombings showed they hit their intended targets.

Defense Department (web) press secretary Geoff Morrell said it was too early to know whether the strike killed the 11 Pakistani troops.

"Every indication we have is that this was a legitimate strike against forces that had attacked members of the coalition," he said.

Pakistan army spokesman Maj. Gen. Athar Abbas gave a different account.

Abbas said the fighting broke out after Afghan government soldiers who had occupied a mountaintop position in a disputed border zone Monday acceded to a Pakistan request to withdraw.

"They were on their way back and they were attacked by insurgents in their own territory," Abbas said.

He said the Afghans then called in coalition airstrikes, which hit the Pakistani Frontier Corps post across the border.

The anti-terror alliance with Washington is already unpopular among Pakistanis, whose newly elected civilian government is negotiating with some militants in hopes of curbing a surge in violence. Western officials fear peace deals could give more space for Taliban and al-Qaida (web|news) militants to operate.