US officials say a drone strike in north-west Pakistan may have killed one of al Qaeda's top strategists.
Abu Yahya al-Libi, a Libyan cleric was a target of the strike by two missiles in North Waziristan tribal region on Monday, but it is unclear if he was among the 15 people killed.
Meanwhile, Pakistan's foreign ministry has summoned the US deputy ambassador to Islamabad to protest over recent drone strikes.
Pakistan maintains the strikes are a violation of its sovereignty.
Washington believes that Libi, an Islamic scholar from Libya, became al-Qaeda's second-in-command following Osama Bin Laden's death last year.
Libi is reportedly in charge of day-to-day operations in Pakistan's tribal areas. He was reported killed in a drone strike in Pakistan in 2009, but it turned out to be a case of mistaken identity.