The International Security Assistance Force confirmed that its helicopters clashed with the al Qaeda-linked Haqqani Network near the Pakistani border, but would not confirm the aircraft crossed into Pakistan to conduct attacks.

Ten Haqqani Network fighters fighters were killed during a clash this morning along the border between Afghanistan and Pakistan, a US military official told The Long War Journal, but current reports indicate the helicopters did cross into Pakistan to engage Taliban fighters. The military official said that ISAF is still gathering information on the clash.

The fighting took place near Combat Outpost Narizah, an Afghan base just eight miles from the Pakistani border in Khost province, the official said. Khost is a stronghold of the Haqqani Network, an Afghan Taliban subgroup based in North Waziristan, Pakistan.

The statement played down reports from earlier today that indicated US helicopters killed five insurgents as they fled into Pakistan's tribal agency of Kurram, which borders Khost. In another report, a Pakistani security official claimed that US helicopters crossed the border and struck a local checkpoint manned by members of "noble tribal families."

Combat Outpost Narizah was the scene of two major clashes over the weekend that resulted in US helicopters pursuing Haqqani Network fighters into Pakistan's Taliban-controlled tribal agency of North Waziristan. Initial reports indicated that more than 30 Haqqani Network fighters were killed in the two cross-border engagements, but later reports state than between 50 to 60 may have been killed.

Pakistan objects to weekend's cross-border raids from Afghanistan

ISAF has maintained that it legitimately attacked Taliban forces as part of an existing policy of hot pursuit of fighters.

US forces pursued the Taliban into Pakistan "after following the proper rules of engagement under inherent right of self defense," Master Sergeant Matthew Summers, an ISAF spokesman, told The Long War Journal on Sept. 26.

But a spokesman at Pakistan's Foreign Office rejected reports that such an agreement between ISAF and Pakistan exists, and said the incursions are a violation ISAF's mandate.

“These incidents are a clear violation and breach of the UN mandate under which ISAF operates,” spokesman Abdul Basit said in a statement released by the Foreign Office, according to AFP.

“There are no agreed 'hot pursuit' rules," Basit continued. "Any impression to the contrary is not factually correct. Such violations are unacceptable. In the absence of immediate corrective measures, Pakistan will be constrained to consider response options."

Background on agreement on cross-border activities between ISAF and Pakistan

Although the Pakistani Foreign Office denied the existence of any agreement that permits ISAF forces to enter Pakistan while in hot pursuit of Taliban fighters, the details of such an agreement have been known for years. In August 2007, The Associated Press released the text of the agreement.

The agreement between ISAF and Pakistan stipulated the following: US forces must be engaged with the Taliban or al Qaeda as they cross into Pakistan; US forces should not penetrate more than six miles into Pakistani territory; and US forces may enter Pakistan if they have identified the location of Osama bin Laden, Ayman al Zawahri, or Mullah Omar.

The US has pursued Taliban fighters across the border multiple times. Two of the most high-profile incidents occurred in 2008. The first took place in June 2008, when US troops pursued a Taliban force from Kunar into Pakistan's tribal agency of Mohmand, and killed 11 fighters. The Pakistani government claimed that the US killed Frontier Corps troops, but the US released video of the incident showing the Taliban being targeted as they fled from Kunar into Mohmand. Pakistan's paramilitary Frontier Corps is known to support the Taliban in Afghanistan.

The second incident took place in Khyber in November 2008, when US forces launched rocket attacks and ground strikes into the Tirah Valley, a known haven for al Qaeda, the Taliban, and the Lashkar-e-Islam. Seven people were reported killed and three were wounded in the strikes.

The US also launches covert airstrikes using unmanned Predators and Reapers against al Qaeda and the Taliban in Pakistan's tribal areas. The Pakistani government officially protests the covert strikes but quietly approves. Three such strikes have been launched inside Pakistan over the past three days; all have taken place in North Waziristan.