PESHAWAR, Pakistan, (Reuters) – Rescuers scoured the wreckage of Peshawar’s top hotel for victims on Wednesday after a suicide bomb killed at least seven people, the latest militant attack in retaliation for a Pakistani army offensive in the Swat valley.

The resolve shown by the Pakistani government and military in Swat has heartened U.S. officials, concerned their nuclear-armed ally could slide into chaos unless the Taliban’s creeping advance toward Islamabad was stopped.

A U.N. official said two U.N. workers, a Russian man and Philippine woman, were among those killed in the Tuesday night assault on the Pearl Continental, a hotel popular with VIPs and foreigners visiting the capital of North West Frontier Province.

Taliban militants have stepped up attacks in cities since the army launched a campaign in April to clear Islamist fighters from a stronghold in Swat and other parts of northwest Pakistan.

“We have the death toll of seven people killed in the blast including four whose bodies were recovered today,” said city police chief Sifwat Ghayyur, the head of the investigation.

The toll excludes dead militants and people still missing in the ruined hotel. The force of the blast blew out all its windows, and caused several concrete walls and a section of floors to collapse on the hotel’s front side.

Senior police official Abdul Gafoor Afridi said 64 people were wounded. The hotel manager was among those missing.

Militants had shot their way into the hotel forecourt and exploded a truck bomb in front of the lobby, evoking nightmarish memories of the attack on the Marriott hotel in Islamabad last September that killed 55 people.

News channels ran closed circuit television camera footage from the checkpoint at the hotel entrance on the main road.

It showed a cyclist brushing aside a security guard, who then returned to his cabin. As the cyclist pedalled through, a retractable metal barrier in the driveway was lowered, and a saloon car pulled into the entrance. There appeared to be shots fired, before the car sped over the lowered barrier towards the hotel, swiftly followed by a small truck. Another guard ran for cover as the shots were fired.

Police said the bomb contained 500 kg (1,100 lb) of explosives, a similar size to the bomb at the Marriott.

The mangled truck used in the attack could be seen several feet away from the crater caused by the explosion. There was no claim of responsibility, but the Taliban have warned of retaliation because of the Swat offensive, and there has been a new trend in militant tactics towards using gunmen in support of a suicide bomber.

There are expectations the army will turn its attention to other Taliban strongholds, like the South Waziristan tribal region bordering Afghanistan, once Swat has been dealt with.

Military gunship helicopters pounded militant positions on Wednesday in the Jani Kheil area of Bannu, a district at the gateway to Waziristan.

“The operation is underway in Jani Kheil. Gunships, artillery and ground troops are being used in the operation,” a military official said on condition of anonymity. He said the militants had suffered casualties, but no tally was available. Waziristan is regarded as one of the main sanctuaries for Taliban factions involved in the Afghan insurgency, and a hiding place for al Qaeda fighters plotting attacks in the West.

Pakistan’s decision to opt for military action has been helped by a shift in public opinion.

That support might ebb if the welfare of some 2.5 million people displaced by the conflict in the northwest is mishandled. U.S. officials are rallying international support to help Pakistan cope with the humanitarian crisis. The military says troops have cleared most of Swat, but soldiers are encountering pockets of resistance.

In all, the army says more than 1,300 militants and 105 soldiers have been killed in the offensive. There has been no independent confirmation of the figures.

The United Nations is heavily involved in providing relief for the people who have fled their homes to escape the conflict in Swat, and about a dozen U.N. staff were staying at the Peshawar hotel.

A German woman also working for the U.N. children’s fund, and a British and a Nigerian man were wounded, according to top city administrator Sahibzada Anis. Less than a third of the hotel’s 150 rooms were occupied.