Pakistani authorities have closed a major supply route for NATO troops fighting in Afghanistan in apparent retaliation for the killing of three Pakistani soldiers by NATO aircraft involved in a cross-border pursuit.
A statement from ISAF, the International Security and Assistance Force, said two helicopters initially crossed the border in the Kurram region briefly today while targeting suspected insurgents who had been firing on a coalition base from a position inside Afghanistan.
After the aircraft received fire from a position inside Pakistan, they re-crossed the border to target their attackers.
The statement said the pilots were "operating in self-defense" and "[killed] several armed individuals."
Hours after the incident, trucks and fuel tankers destined for foreign forces' positions in Afghanistan were stopped at the Torkham border post in the Khyber tribal region near the city of Peshawar.
RFE/RL's Radio Mashaal confirmed that Pakistani authorities had closed the post to NATO vehicles.
At the U.S. State Department, spokesman Philip Crowley downplayed the significance of the incident. "ISAF is working with the Pakistani government to investigate the incident earlier today," he said.
"We have multiple routes to be able to resupply our forces in Afghanistan. We are aware of, I think, one gate being closed and we're discussing that with the Pakistani government," Crowley added.
In a statement that reflected Islamabad's impatience, the Pakistani military said, "This is the third incident of its kind during the past week."
Pentagon spokesman Colonel David Lapan noted that the Pakistani statement said its forces "used rifle fire at the helicopters as a warning."
"You fire at helicopter in a combat zone, they usually take that as hostile and return fire," he said.
Lapan also said the Torkham border crossing closure had had "no immediate impact" on NATO resupply, but that could change if it remains closed. The bulk of non-lethal military supplies for NATO troops in Afghanistan pass through Pakistan.
Pakistan is a crucial ally for the United States in its efforts to stabilize Afghanistan, but analysts say border incursions and disruptions in NATO supplies underline growing tensions in the relationship.
The United States has recently increased the number of missile strikes by pilotless drone aircraft on militant targets inside Pakistan. In September there were 21 strikes, the highest monthly total since the strikes began in 2008.
The State Department's Crowley said the United States "takes seriously [its] responsibilities as a partner" to Pakistan.
with agency material and RFE/RL's Radio Mashaal