U.S. ambassador to Pakistan Anne Patterson visits the mausoleum of Mohammad Ali Jinnah, founder of the nation, in Karachi October 22, 2007. REUTERS/Athar Hussain

ISLAMABAD (Reuters) - Pakistan summoned U.S. ambassador Anne Patterson on Thursday to receive a formal protest over missile strikes launched by pilotless drone aircraft against militant targets on Pakistani soil, a Pakistani foreign ministry official said.

The protest came a day after a suspected U.S. missile strike killed five militants, possibly including an Arab al Qaeda operative.

Wednesday’s attack on Bannu district was unusual in that it took place deeper in Pakistani territory in an area outside the semi-autonomous tribal lands bordering Afghanistan where most other attacks have focused.

“The American ambassador has been called to the Foreign Office to lodge a protest over the missile attack in Bannu,” a Foreign Ministry official told Reuters.