ISLAMABAD, Pakistan (AP) -- Rescuers pulled more bodies from the shell of the truck-bombed Marriott Hotel in Pakistan's capital Sunday, pushing the death toll from one of the country's worst terrorist strikes to 53, including the Czech ambassador and two Americans.
The five-story hotel, a favorite spot for foreigners and the Pakistani elite - and a previous target of militants - still smoldered from a fire that raged for hours after the previous day's explosion, which also wounded more than 250 people.
No group immediately claimed responsibility, though suspicion fell on al-Qaida and the Pakistani Taliban. IntelCenter, a U.S. group that monitors and analyzes militant messages, noted that al-Qaida's 9/11 anniversary video threatened attacks against Western interests in Pakistan, where many are angered by a wave of cross-border strikes on militant bases by U.S. forces in Afghanistan.
The bomb went off close to 8 p.m. Saturday, when the restaurants inside would have been packed with Muslim diners breaking their daily fast during the holy month of Ramadan.
The owner of the hotel accused security forces of a serious lapse in allowing a dump truck to approach the hotel unchallenged and not shooting the driver before he could trigger the explosives.
"If I were there and had seen the suicide bomber, I would have killed him. Unfortunately, they didn't," Sadruddin Hashwani said.
The government released footage from a hotel surveillance camera showing the heavy truck turning left into the gate at speed, ramming a metal barrier and coming to a halt about 60 feet away from the hotel.
Guards nervously came forward to look, then scattered after an initial small explosion.
Several guards tried repeatedly to douse flames spreading through the cab of the truck as traffic continued to pass on the road behind. There is no sign of movement in the truck and the footage played did not show the final blast.
Prime Minister Yousuf Raza Gilani said the bomber attacked the hotel only after tight security prevented him from reaching Parliament or the prime minister's office, where the president and many dignitaries were gathered for dinner.
"The purpose was to destabilize democracy," Gilani said. "They want to destroy us economically."
Officials said vehicles carrying construction materials are allowed to move after sunset, meaning the sight of a dump truck near the government quarters might not have aroused suspicion.
Rescue teams searched the blackened hotel room by room Sunday, but the temperatures remained high, and fires were still being put out in some parts. Officials feared the main building would collapse.
Interior Ministry chief Rehman Malik said the bomb contained an estimated 1,300 pounds of military-grade explosives as well as artillery and mortar shells and left a crater 59 feet wide and 24 feet deep in front of the main building.
Khalid Hussain Abbasi, a rescue official, confirmed that six new bodies had been found, but would not say if the dead were foreigners. He said he expected more charred remains to be discovered.
Gilani said the death toll had reached "about 53" and that Czech Ambassador Ivo Zdarek was among the dead. Zdarek, 47, only moved to Islamabad in August after four years as ambassador to Vietnam.
Malik said two Americans were confirmed dead as well as one Vietnamese national. Officials in Pakistan said at least 21 foreigners were among the wounded, including Britons, Germans, Americans and several people from the Middle East.
TV footage showed at least two bodies partially visible from the wrecked facade Sunday morning. Outside, the hotel was surrounded by torched vehicles and debris.
The bombing came just hours after President Asif Ali Zardari made his first address to Parliament, less than a mile away from the hotel. Malik said authorities received intelligence there might be militant activity linked to Zardari's address and security had been tightened.
The attack drew condemnations from around the world, including the United States, which has pressured Pakistan to do more to wipe out militant hide-outs on its side of the Afghan border. Washington worries about Taliban and al-Qaida fighters using Pakistan as a training, recruiting and regrouping ground to aid the insurgency in Afghanistan.
President Bush said the attack was "a reminder of the ongoing threat faced by Pakistan, the United States, and all those who stand against violent extremism."
A recent series of suspected U.S. missile strikes and a rare American ground assault in Pakistan's northwest have signaled Washington's impatience with Pakistan's efforts to clear out militants. But the cross-border operations have drawn protests from the Pakistani government, which warned they would fan militancy.
Terrorism researcher Evan Kohlmann told the AP the attack was almost certainly the work of either al-Qaida or the Pakistani Taliban.
"It seems that someone has a firm belief that hotels like the Marriott are serving as 'barracks' for Western diplomats and intel personnel, and they are gunning pretty hard for them," Kohlmann said.
The Marriott blast could prompt diplomats and aid groups in Islamabad, some of whom already operate under tight security, to re-evaluate whether nonessential staff and family members should stay. U.N. officials met Sunday to discuss the security situation and, for now, made no decision to change their measures, said Amena Kamaal, a spokeswoman.
Zardari, who on Sunday was headed to New York to lead a delegation to the United Nations and was expected to meet with Bush during the week, spoke out against the cross-border strikes in his speech to Parliament. He condemned the "cowardly attack" afterward in an address to the nation.
"Make this pain your strength," he said. "This is a menace, a cancer in Pakistan which we will eliminate. We will not be scared of these cowards."
In January 2007, a security guard blocked a suicide bomber who triggered a blast just outside the Marriott, killing the guard and wounding seven other people.
The country's deadliest suicide bombing was on Oct. 18, 2007, and targeted ex-Prime Minister Benazir Bhutto - Zardari's wife - who survived. It killed about 150 people in Karachi during celebrations welcoming her home from exile.
Bhutto was assassinated in a subsequent attack on Dec. 27, 2007.
On Aug. 21, 2008, suicide bombers blew themselves up at two gates into a mammoth weapons factory in the town of Wah, killing at least 67 people and wounding more than 70.
Associated Press writer Nahal Toosi, Stephen Graham and Asif Shahzad contributed to this report.