NATO helicopters from Afghanistan intruded into northwest Pakistan and attacked a military check post near the border on Saturday, killing up to 25 troops and wounding 14, Pakistani military officials told Reuters.
A senior Pakistani military officer said efforts were under way to bring the bodies to the headquarters of Mohmand tribal region from their post located on hilltops near the Afghan border.
"The latest attack by NATO forces on our post would have serious repercussions as they without any reason attacked on our post and killed soldiers asleep," he said, requesting anonymity because he was not authorized to talk to the media.
The Associated Press reported that Pakistan state TV had reported the same death toll, amid earlier conflicting reports.
A Pakistani military spokesman confirmed the pre-dawn attack in the tribal region of Mohmand and said casualties had been reported, but gave no details.
"NATO helicopters carried out an unprovoked and indiscriminate firing on a Pakistani check post in Mohmand agency, casualties have been reported and details are awaited," the spokesman told Reuters.
Pakistan's Prime Minister Yousaf Gilani strongly denounced the attack, according to a message on Twitter by Radio Pakistan.
The governor of Pakistan's northwest Khyber Pakhtunkhwa province criticized the incident, calling it "an attack on Pakistani sovereignty."
NATO supplies suspended
Journalist Ahmad Mukhtar said in a message on Twitter that Pakistan was suspending NATO's truck supplies that travel through Pakistan to Afghanistan.
Reuters, citing Pakistani officials, later reported that trucks and fuel tankers were stopped at Jamrud town in the Khyber tribal region near the city of Peshawar, hours after the raid.
"We have halted the supplies and some 40 tankers and trucks have been returned from the check post in Jamrud," Mutahir Zeb, a senior government official, told Reuters.
Another official said the supplies had been stopped for security reasons.
The Salala check post, about 1.5 miles from the Afghan border, was recently set up by the Pakistan army to stop Taliban militants holed up in Afghanistan from crossing the border and staging attacks, officials told The Associated Press.
The attack took place around 2 a.m. local time in the Baizai area of Mohmand, where Pakistani troops are engaged in fighting Taliban militants.
Various unnamed officials had previous put the death toll at between seven and 13.
A spokesman for the NATO-led International Security Assistance Force in Kabul said the coalition there was aware of "an incident."
In a message on Twitter, ISAF said it was "Currently gathering info in [sic] that incident."
The attack comes as relations between the United States and Pakistan, its ally in the war on terror, are already strained following the killing of al-Qaida leader Osama bin Laden by U.S. special forces in a secret raid on the Pakistani garrison town of Abbottabad in May.
U.S. helicopters accidentally killed two Pakistani soldiers near the border last year, prompting Pakistan to temporarily close the border to supplies shipped through the country to NATO troops in Afghanistan.