The Pakistani government is claiming that a NATO attack on two checkpoints near the Afghanistan border has killed 24. In response Pakistan has closed both border crossings with Afghanistan, effectively halting the path of NATO supply trucks into the country.

Details of the attack are still sketchy, but the Pakistan government is saying that the attacks were unprovoked, a sentiment that wasn't dispelled by an unnamed Western diplomat who spoke to CBS News. "We don't know the full details yet," the diplomat said. "But it's possible the attack may have mistakenly targeted Pakistani soldiers on the assumption that they were militants."

NATO has said that they are investigating the incident which occurred just before dawn. Insurgents based across the Pakistan border are responsible for much of the violence in Afghanistan, but NATO forces are not allowed to cross over to attack them.

Regardless of how events unfolded, the incident will only further strain already fraught relations between Pakistan and Western forces. "How can anyone expect a regime in Islamabad to be giving more support to the U.S. when our soldiers are being killed in cold blood?" a senior Pakistan foreign ministry official asked CBS News.

The attacks come nearly a year after two Pakistani were killed after being mistaken for insurgents by U.S. helicopter pilots.