A suicide truck bomber attacked the Marriott Hotel in Islamabad, killing at least 40 people, wounding nearly 250 and starting a fire that swept through the building in the Pakistani capital.
The explosion came hours after new President Asif Ali Zardari, widower of assassinated former prime minister Benazir Bhutto, made his first address to parliament a few hundred metres away, calling for terrorism to be rooted out.
As flames engulfed the tightly guarded hotel, part of a US chain and popular with foreigners, diplomats and rich Pakistanis, police said there were still people trapped inside.
Mr Zardari made a televised address to the nation and said the bombing was a cowardly attack which came as the country was celebrating democracy.
The attack was the worst in the capital and came six months after a civilian government took power and a month after it forced former army chief Pervez Musharraf to step down as president.
A crater up to six metres deep was in the road in front of the hotel's gates. The Interior Ministry said the bomb probably contained more than 500 kg of explosives.
The ministry said two foreigners were killed and hospital officials said at least five were wounded. They included a Danish diplomat, the Danish Foreign Ministry said. Up to six Saudi Arabians were missing, the Saudi ambassador said.
A security official said one American was killed.
The Interior Ministry said 236 people had been wounded.
