Pakistan ? A suspected American missile strike killed five alleged militants in northwestern Pakistan early today, an intelligence official said, the fourth attack in 24 hours as the U.S. steps up the tactic to keep al-Qaida and its allies under pressure.

The barrage against houses and a vehicle in the mountains close to the Afghan border was one of the most intense since the attacks were stepped up more than two years ago. Most are believed to be fired from unmanned, remote-controlled planes that can hover for hours above the area.

U.S. officials do not publicly acknowledge the strikes but have said privately that they have killed several senior Taliban and al-Qaida militants and scores of foot soldiers in a region largely out of the control of the Pakistani state.