DERA ISMAIL KHAN, Pakistan — A suspected American missile strike  killed five alleged militants in northwestern Pakistan early Thursday,  an intelligence official said, the fourth such attack in 24 hours.
The  barrage of suspected U.S. missiles 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 in a bid to keep  pressure on al-Qaida and its allies. Most are believed to be fired from  unmanned, remote-controlled planes that can hover for hours above the  area.
Also Thursday, 10 people were killed close to the Afghan  border in Kurram region when a roadside bomb hit the bus they were  traveling in, said local government official Noor Ahmed. It was unclear  why — or whether — the vehicle was targeted.
U.S. officials do not  publicly acknowledge the missile 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. Critics say innocents are also killed, fueling support  for the insurgency.
The latest attack took place before dawn on a  house close to a disused match factory a little more than a mile (three  kilometers) west of Miran Shah town, a hub for local and international  militants in the North Waziristan region, an intelligence official said.  He spoke on condition of anonymity in line with the policy of his  agency. Five alleged militants were killed, he said.
The three  attacks Wednesday also took place in North Waziristan, a lawless region  home to al-Qaida leaders plotting attacks in the West, insurgents  battling foreign troops just across the border in Afghanistan and  extremists behind bombings in Pakistan. There have been at least four  other attacks over the last week.
Pakistani intelligence officials  working from army bases in North Waziristan have a network of spies who  inform them of the attacks. Sometimes journalists are able to speak by  phone to villagers who witness them. Pakistan security agencies are  believed to cooperate with at least some of the strikes, but there is  very little independent reporting of them because the region is so  dangerous for outsiders.
The names of those killed are rarely released, and allegations of civilian casualties are not publicly investigated.
The  militants have stepped up their own attacks in Pakistan in recent days,  just as the army focuses on helping millions of victims from the worst  floods in the country's history. Four big bombs have killed at least 135  people in less than a week.
Pakistan's army has launched several  offensives in the northwest over the last two years, but has resisted  moving into North Waziristan despite U.S. pressure. A major militant  faction there, the Haqqani network, is blamed for attacks against U.S.  troops in Afghanistan but has refrained from striking inside Pakistan.  Analysts believe the army views the network, with which it has  historical links, as an important tool to secure its interests in  Afghanistan once foreign troops withdraw.