Investigators searched a wrecked luxury hotel in northwestern Pakistan for evidence Wednesday after a brazen suicide bombing killed 11 people, including aid workers, in what the U.N. condemned as a "heinous terrorist attack."

Elsewhere in the volatile region, security forces killed 70 suspected militants in an area close to two major Taliban tribal strongholds, intelligence officials told The Associated Press.

No one immediately claimed responsibility for late Tuesday's bombing of the Peshawar Pearl Continental, but the blast followed Taliban threats to carry out major attacks in large cities to avenge an army offensive against insurgents in the nearby Swat Valley.

The government is trying to build public support for offensives against the Taliban, and reaction was swift with calls for harsh punishment for the attackers.

"This is a war, but the people of this country will not bow to the cowardly acts of terrorists. People are now seeing the real face of those who have been exploiting them in the name of Islam," North West Frontier Province senior minister Bashir Ahmad Bilour told reporters. "We will fight this war till our last breath. They cannot break us. The whole nation is united."

Mohammad Zubair, 32, a human resource employee with a construction company in Lahore, called the Taliban "a mafia of criminals" who deserve the strongest possible action by the government.

"They do not have anything to do with Islam. They are just exploiting our religion to mislead our youth," he said. "They are killing innocent people. They deserve death wherever they are."

At least three suicide attackers shot their way past guards and set off the explosion outside the hotel, a favorite spot for foreigners and well-off Pakistanis and a site that the U.S. was considering for its consulate.

The attack reduced a section of the hotel to concrete rubble and twisted steel and left a huge crater in a parking lot. Senior police official Safwat Ghayur said counterterrorism experts, police and intelligence agents were combing the rubble for clues Wednesday.

Security camera footage show the attackers in two vehicles: a white sedan and a small truck. The vehicles pull up to a guard post outside the hotel, with the car in front. A puff of smoke appears near the car window. A guard collapses, apparently shot. The vehicles move into the hotel compound. A flash and eruption of dust follow seconds later.

The truck was carrying more than half a ton of explosives, senior police officer Shafqatullah Malik estimated.

The chaotic scene echoed a bombing last year at Islamabad's Marriott Hotel that killed more than 50 people. Both hotels were favored places for foreigners and elite Pakistanis to stay and socialize, making them high-profile targets for militants despite tight security.

Both hotels are owned by Sadruddin Hashwani, who vowed to rebuild quickly and claimed the government was partly to blame for the attack by not providing better security.

North West Frontier Province senior minister Bashir Ahmad Bilour denied the government was at fault and said closed-circuit TV footage showed the hotel had removed some security barriers.

In Washington, two senior U.S. officials said the State Department had been in negotiations with the hotel's owners to either purchase or sign a long-term lease for the facility to house a new American consulate. The officials said they were not aware of any sign that U.S. interest in the compound had played a role in its being targeted.

The officials spoke on condition of anonymity because the negotiations were not public and had not been completed. They said no immediate decision had been made on whether to go ahead with plans to base the consulate on the hotel grounds.

The exact death toll remained elusive Wednesday.

North West Frontier Province Information Minister Mian Iftikhar Hussain told AP that officials reported 11 fatalities. Other police and government officials could confirm only five dead.

The three attackers also died, said an intelligence official who spoke on condition of anonymity because he was not authorized to speak to the media. U.N. spokeswoman Amena Kamaal said three bodies pulled from the rubble Wednesday were two Pakistani government staffers whose work was funded by the U.N.'s population agency, along with their driver.

The U.N. also identified staff members among the dead — Aleksandar Vorkapic, 44, from Belgrade, Serbia, and UNICEF staffer Perseveranda So, 52, from the Philippines.

U.N. Secretary-General Ban Ki-moon on Tuesday condemned the hotel bombing as a "heinous terrorist attack."

U.N. officials declined to comment Wednesday on whether they might scale back their programs in Pakistan. Such a move could have significant consequences because of a refugee crisis sparked by the military offensive in Swat, where more than 2 million people have been displaced.

"Humanitarian workers around the world are coming under increasing attack, and it is the poor, the uprooted and the vulnerable who will suffer the most by their loss," U.N. High Commissioner for Refugees Antonio Guterres said. "Now, once again, we are forced to ask ourselves, 'How we can meet their urgent needs while ensuring the safety of our own humanitarian staff?' It is a truly terrible dilemma."

Hiro Ueki, a U.N. spokesman in Pakistan, said besides the two U.N. staffers killed, four were wounded.

"We have moved most of the U.N. staff to Islamabad in view of what happened yesterday," he said. "Only a skeleton staff is staying in Peshawar at the moment. We are reviewing the security situation."

Peshawar and other Pakistani towns and cities have weathered a wave of bombings in recent months that has only intensified since the Swat offensive, strongly supported by Washington, began over a month ago.

On Tuesday, the Pakistani military took action in Bannu, a region near Swat, after tribal elders there failed to move against militants in their midst who allegedly helped kidnap more than 100 students from a boys' school who were later freed.

Two intelligence officials said troops, backed by helicopter gunships and artillery, attacked the Jani Khel section of Bannu, leaving some 70 militants dead. They spoke on condition of anonymity because they were not authorized to speak to the media. It was not possible to independently confirm that toll because of the remote, dangerous nature of the region.

Bannu is near both South and North Waziristan, two major strongholds for Al Qaeda and the Taliban. South Waziristan in particular is expected to be the site of an offensive after Swat, though the military has not confirmed any plans.

In the northwest's Upper Dir region, meanwhile, a handful of paramilitary troops joined a tribal militia pursuing Taliban fighters in retaliation for a suicide bombing on a mosque, police said.

Hundreds of tribesmen have been battling the militants since Saturday, most intensely in two villages.

"There were reports of intense fighting last night, but since this morning the militants are not retaliating," police official Rahim Gul said by phone. "It is not like that they have run out of ammunition. They are very clever. They have all the weapons. It could be part of their strategy to drag the militia deeper into the terrain."

Gul said six paramilitary Frontier Corps troops joined the militia Wednesday with responsibility for firing mortar shells against the Taliban targets. At least 14 alleged militants have been killed since Saturday, officials say.