Two Apache attack helicopters from the NATO-led International Security Assistance Force crossed the border from eastern Afghanistan Friday after insurgents attacked a remote Afghan security outpost in Khost province
An ISAF statement Sunday said the helicopters were following the rules of engagement when they crossed into Pakistan.
Pakistani Interior Minister Rehman Malik complained to lawmakers in Islamabad that NATO action inside Pakistani territory was unacceptable, Pakistan's Daily Times newspaper reports.
"This is an attack on our sovereignty," he said. "We will react soon and serve notice on the Afghan ambassador."
The attack killed 30 insurgents along the Pakistani border with Afghanistan.
U.S.-led forces in Afghanistan routinely target al-Qaida and Taliban militants inside Pakistani territory with unmanned drones. U.S. President Barack Obama has sanctioned more drone activity inside Pakistan as part of a broader counter-insurgency campaign.
Piloted attacks inside Pakistani territory carried out by NATO forces, however, are rare.