Police say suspected militants have staged a rare attack in southern Pakistan against trucks carrying supplies for NATO troops in neighboring Afghanistan, wounding three people.

Police official Mohammed Ali says the militants attacked the trucks with guns and grenades early Thursday as they traveled on a main highway on the outskirts of the southern city of Karachi.

Up to 75 percent of the supplies for Western forces in landlocked Afghanistan arrive at Karachi port and then head north.

Militants have carried out a wave of attacks against the supply trucks in northwestern Pakistan near the Afghan border, but such attacks are rare in Karachi.