The blasts occurred at a food distribution point, but there were conflicting reports whether the victims were lining up for food or being registered. The camp is sometimes used by foreign humanitarian groups, including the World Food Program, to deliver aid.

Meanwhile, the Pakistani army admitted that civilians were killed in an airstrike last Saturday in the northwest that supposedly targeted militants. It did not say how many had died, but apologized in a rare acknowledgment of an error that could help reduce anger among local tribes, whose support it needs to defeat the Taliban and al-Qaida.

The two suicide bombers struck six minutes apart at a camp in the Kacha Pukka area of Kohat, a tribally administered region close to the Afghan border. They were dressed in burqas, the all-encompassing veil worn by conservative Muslim women in parts of Afghanistan and Pakistan, local police official Abdullah Khan said.

Government official Dilawar Khan Bangash said 41 people were killed and 62 were wounded in the attack.

Pakistan has been hit by near-daily explosions over the last 18 months blamed on al-Qaida and Taliban militants. Most have been directed at security or government installations, but civilians have also been targeted, sometimes to punish those seen as cooperating with the government.

The camp was for people who fled from the Orakzai district, where the army has been fighting militants since the end of last year. The tempo of the operations has picked since March, with frequent aerial bombardment. The camp housed between 1,000 and 2,000 people.

There was no claim of responsibility, but that is not unusual when bomb attacks kill ordinary Pakistani citizens.

About 210,000 civilians have fled from Orakzai since the end of last year, including nearly 50,000 people who have left in the last month when ground forces moved into the area to flush out insurgents.

There have been fewer bombings in major cities outside of the northwest during the first three months of this year compared to late last year. The slowdown follows a major offensive in the South Waziristan tribal region, where many militants had been based.

The army's apology was for airstrikes in the Khyber region last Saturday that villagers said killed about 70 people.