"BBC": Pakistan accuses NATO forces on carrying out air attacks in the border checkpoint.

Pakistani officials have responded with fury to an apparent attack by NATO helicopters on a border checkpoint they say killed at least 24 soldiers.

The "unprovoked and indiscriminate" attack took place in Mohmand tribal region, the Pakistani military said.

Prime Minister Yousuf Raza Gilani called it "outrageous" and convened an emergency meeting of the cabinet.

NATO's force in Afghanistan is investigating and has offered condolences to the affected families.

The night-time attack took place at the Salala checkpoint, about 1.5 miles (2.5 km) from the Afghan border, at around 02:00 local time (21:00 GMT). A statement from the Pakistani army said 24 people were killed and 13 were injured.

Prime Minister Gilani cut short a visit to his hometown to return to Islamabad, where he called an emergency meeting of the cabinet.

A foreign ministry statement said he was taking up the matter with NATO and the US "in the strongest terms".

Within hours of the alleged attack it was reported Pakistan had closed the border crossing for supplies bound for NATO forces in Afghanistan-a move which has been used in the past as a protest.

The BBC's Syed Shoaib Hasan in Karachi says furious Pakistani officials insist there was no militant activity in the area at the time.

The incident looks set to deal a fresh blow to US-Pakistan relations, which had only just begun to recover following a unilateral US raid that killed Osama Bin Laden in Pakistan in May.