At least four people were killed on Friday afternoon when a U.S. drone struck in the North Waziristan tribal agency in northwest Pakistan near the Afghan border, local sources said.

The pilotless aircraft fired missiles into a village in Mir Ali, also injuring two people, they said.

Details about the killed are not immediately known. But most of the killed are believed to be militants hiding in the area.

Friday's strike is the 9th of its kind since October. So far a total of 70 people have reportedly been killed in the U.S. drone shelling this month.

Most of the people targeted by the U.S. drones are militants, but the U.S. drones do sometimes mistakenly kill innocent civilians.