Pakistan has blamed the US for an airstrike that killed at least 11 of its troops on the Afghan border.
Two aircraft bombed several locations, hitting two Frontier Corps paramilitary posts in the Mohmand tribal region, local tribesmen said.
A military official said the airstrike was from a drone launched from Afghanistan.
An army statement said the incident “had hit at the very basis of cooperation” between the two countries in the war on terror.
It said a strong protest has been launched by the Pakistan army, which reserved “the right to protect our citizens and soldiers against aggression.”
The United States has in the past used unmanned drones to attack suspected militants inside Pakistan, an ally in its war on terror. Pakistan says the attacks are a violation of its sovereignty.
US Forces in Afghanistan refused to comment on the incident today.
Pakistani TV networks also reported the incident but gave varying accounts of the death toll and the fighting, which took place in a far-flung border area known as Speena Sooka, or White Peak.
State-run Pakistan Television said 18 people died, including 10 troops and eight civilians. It reported that Afghan and foreign forces had tried to set up a military post and were resisted by tribesmen. A Nato airstrike then struck a Pakistani military post, PTV said.
Pakistan says it has deployed tens of thousands of troops to police its tribal regions, but Afghan and Nato officials say that militants still use the lawless area as a staging post for attacks inside Afghanistan.