Hundreds of people were wounded in the blast [Reuters]

Rescue workers are searching through the smouldering remains of the Marriott hotel in Islamabad after a lorry-bomb attack killed at least 53 people and left more than 200 injured.

Recovery teams pulled out at least four more bodies on Sunday and feared that more would be found in the wreckage of the hotel.

The interior ministry said that two Americans were among those killed. Ivo Zdarek, the Czech ambassador, was also killed in the attack.

He called his embassy moments after Saturday night's bombing from inside the hotel asking to be rescued, but officials confirmed later on Sunday that he had died in the blast.

Officials said they were worried that the building, which burned through the night after Saturday's blast ruptured a gas pipeline, might collapse.

Eleven foreigners were killed in the attack.

Blast investigated

Hundreds of armed police and soldiers ringed the scene in the Pakistani capital, while army bulldozers cleared rubble from nearby streets.

"It has the hallmarks of al-Qaeda," a senior official involved in the investigation said.

"It was an al-Qaeda-style bombing and was similar to the attack on the Federal Investigation Agency office," he said, referring to a suicide attack in March in the eastern city of Lahore which left 20 people dead.

Al-Qaeda-linked fighters have been held responsible for scores of bombings across Pakistan this year that have left more than 1,300 people dead.

Investigators said the bomb used more than 500kg of high-intensity explosives and later on Sunday the interior ministry released video footage from a security camera that showed the moments before a truck carrying the explosives detonated outside the hotel.

Al Jazeera's Imran Khan reported that rain was hampering the work of forensics teams scouring the crater for evidence.

Attack condemned

The hotel bombing came shortly after Asif Ali Zardari, Pakistan's new president, delivered his inaugural address to parliament only a few hundred metres away.

Zardari's administration faces a struggle against al-Qaeda and pro-Taliban fighters in the country's northern tribal regions.

"Terrorism is a cancer in Pakistan, we are determined, God willing, we will rid the country of this cancer," Zardari said in a televised address to the nation. "We will not be deterred by these cowards."

Zardari has left Pakistan for a scheduled meeting with George Bush, the US president.

Al Jazeera's Khan reported that Pakistan's new president was coming under criticism for leaving his country in the aftermath of the hotel blast.

The US administration, which is waging its so-called "war on terror" against al-Qaeda and fighters associated with the group, condemned the "terrorist bombing" saying it was "part of a continuing assault on the people of Pakistan".

Islamabad's Marriott hotel, part of an American-owned chain, was a popular gathering place for foreigners and Pakistan's elite.

Maximum casualties

Pakistan has supported US efforts to tackle al-Qaeda-linked groups, but the conflict is unpopular at home.

Resucers fear the death toll from the blast may rise [Reuters]

Zafar Jaspal, a professor of international relations at the Quaid-i-Azam university in Islamabad, told Al Jazeera: "Since the beginning - I mean since 9/11 happened and Pakistan joining this 'war on terrorism' - the public was divided in Pakistan about whether we should be allied with the 'war on terrorism' or not.

"But in yesterday's attack, it was purely, purely civilian facilities and civilians who were targeted, so I think the sympathies which the public had are now touching their lowest [point] and people are going to follow the government policies on terrorism."

The Marriott attack appeared to have been timed to cause the maximum number of casualties, coming as the hotel was busy with families having their evening meal to break the Ramadan fast.

'Deafening noise'

Mohammad Jamil, who witnessed the explosion, said that a truck exploded just outside the heavily-secured hotel's gates.

He said the force of the blast sent the truck flying into the air and knocked him over on to the street.

"For a few seconds I was in shock and did not know what had happened. Then I remembered the deafening noise," Jalil said.

The blast, so powerful it was heard for miles, blew an enormous crater in the ground and destroyed the outside wall of the compound.

Buildings several kilometres away had windows blown out from the impact.

The streets around the hotel in the centre of the city were littered with burned out vehicles, crumpled furniture and other debris, while trees were snapped in half.

A security official said many people leapt to their deaths from upper floors as the building burned.