"The injured and the dead bodies have been retrieved. The troops are still holding on to the post."
But Pakistani officials said Afghan forces tried to capture parts of the Soran Dara area, which borders the Afghan province of Nangarhar and which Pakistan claims is its own territory.
"There is confusion over what happened," Kamal Hyder, Al Jazeera's correspondent in Islamabad, said.
"Officials have confirmed that Pakistani troops were killed … in an area where Americans and Afghans were conducting joint operations."
Damagh Khan Mohmand, a local tribesman who witnessed the outbreak of fighting late on Tuesday, said the clashes lasted for four hours.
He said Afghan and foreign forces traded fire with both Pakistani tribesmen and troops.
Two aircraft then bombed several locations, hitting two Frontier Corps posts, Khan Mohmand said.
Ten Pakistani paramilitary troops died in the exchange of fire and air raid, a military official in northwestern Pakistan said.
|Afghan forces receive training and operational |
support from the US-led coalition [AFP]
Hyder said the incident was not the first attack on a Pakistani military post.
"A little over a month ago there was an attack at a post not far from Chopara checkpoint," he said.
"Al Jazeera sources in Kabul say that the Nato-led coalition is investigating. The coalition has not released any official statements; nor has the Pakistani military.
"There has been anger from the tribal groups, who have an armed group. They are now saying they will retaliate across the border for the strike."
A series of missile attacks have been attributed to US-led forces in Afghanistan in recent months.
More than a dozen people were killed in one such incident in the tribal region of Bajaur in May.
There have been several disputes over the 2,500km Pakistan-Afghanistan border recently.
Both countries, whose governments are both allies of the US in its so-called "war on terror", have also argued over how to tackle fighters loyal to the Taliban.
Foreign forces within the Nato-led coalition and the government in Kabul have alleged that Pakistan is not being tough enough on the opposition fighters.
Pakistan's new government entered peace talks with Taliban loyalists shortly after allies of Pervez Musharraf, Pakistan's president, were beaten in recent elections.