Al-Qaeda's operations chief in Pakistan and another top aide are believed to have been killed, US sources say.
Usama al-Kini and his lieutenant, Sheikh Ahmed Salim Swedan, were both killed in recent days, US counter-terrorism officials said.
Unconfirmed reports say the two men were killed by a missile fired by a US drone near the Afghan border.
Kini was believed to be behind last year's deadly attack on the Marriott hotel in Islamabad, they said.
Fifty-five people were killed when a truck packed with explosives rammed the hotel in September 2008.