Pakistan ? The U.S. military apparently struck at Islamic militants outside Pakistan’s lawless tribal belt for the first time Wednesday, firing a missile that killed six suspected insurgents taking refuge away from the conflict zone along the Afghan border.

The government denounced the attack as yet another “grave provocation” amid a series of U.S. military operations in the country that have enflamed widespread anger among ordinary Pakistanis.

The harsh words were a sharp contrast to comments Tuesday by U.S. and NATO officials who reported increased cooperation from Pakistan in the fight against militant groups. Tens of thousands of U.S. and NATO troops are stationed in neighboring Afghanistan.