Thirteen militants were killed in an overnight clash near the Afghan border, a U.S. military official told Fox News.

The clash occurred when a militant group apparently came across the border with Pakistan and attacked an Afghan Border Police position.

The Afghan Border Police were engaged in a prolonged firefight and contacted the nearby U.S. Combat Outpost. U.S. air strikes were then called in.

U.S. soldiers at the scene recovered numerous heavy weapons in addition to finding the bodies.

The Afghan Border police as well as Afghan Army and Afghan Police are training and conducting operations with the U.S. Army in the area.

Cross border strikes by the dangerous "Haqqani" faction of the Taliban are frequent. The group has close links to Al Qaeda.

Fox News' Greg Palkot contributed to this report.