In the Muslim tradition, the victims were buried immediately, CBS News correspondent Elizabeth Palmer reports.
Many of the victims were Islamabad Marriot Hotel staff who had been on duty when the bomb went off just after 8 p.m. on Saturday.
Pakistan's Information Minister, visiting some of the 250 wounded in the city's hospitals, vowed her government is more committed than ever to rooting out terrorism.
"We will not step back from the challenge we have undertaken," said Information Minister Sherry Rehman. "The government will root out terrorism at its heart."
But it's going to have to try harder.
Video from the hotel's security cameras shows the large explosives-packed truck arrive at the Marriott, entirely undetected by Pakistan's secret services.
After it rams the security barrier, whole minutes tick by, before a small blast, said to be the suicide bomber detonating a grenade.
A brave guard tries to put the fire out. Then gives up before the whole truck explodes, destroying the hotel.
So who planned this carnage?
So far, no one has claimed responsibility. But both the Pakistani and U.S. governments say the attack shows hallmarks of Al Qaeda, though they acknowledge that could implicate any number of extremist groups, some of them allied with the Taliban on Pakistan's rugged border with Afghanistan, and all of them at war with the Pakistani army, NATO and US troops.
Tonight what's left of the Islamabad Marriott Hotel is an eerie and charred ruin, Palmer reports from Pakistan. Rescue crews say they think they have all the bodies out now but this story is far from over. The blast shocked Pakistan to its very core and has dramatically raised the stakes in its fight against terrorism.
Rescuers continued to pull bodies from the shell of the hotel on Sunday, including the Czech ambassador.
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.
The targeting of the American hotel chain came at a time of growing anger in the Muslim nation over a wave of cross-border strikes on militant bases in Pakistan by U.S. forces in Afghanistan.
Analysts said the attack served as a warning from Islamic militants to Pakistan's new civilian leadership to stop cooperating with the U.S.-led war on terror.
Prime Minister Yousuf Raza Gilani said the bomber had 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."
On Sunday Pakistan announced measures to beef up security across the country under a new plan for big cities which will go into effect beginning Monday, reports CBS News' Farhan Bokhari.
The new security plan appears to be an effort to prevent a recurrence of the kind of attack that targeted the Marriott which has shaken the foundations of Pakistan's ruling establishment.
Rehman Malik, the adviser on interior affairs to prime minister Yusuf Raza Gilani - a position that makes Malik the de facto interior minister - said that the evidence so far gathered from the scene of Saturday's attack point towards the involvement of the Taliban movement, which has its stronghold in the southern part of the Waziristan region, along the Afghan border.
Malik said that Saturday's attack was caused by the use of about 600 kilograms of explosives. The effect of the attack became greater as the bomber also packed the explosives with aluminum powder and artillery rounds, which added significantly to the effect of the explosion, and caused a fire with soaring temperatures after the attack.
In response to a question on a reported U.S. offer to send an FBI team to assist Pakistan with the investigations, Malik said; "We don't need any help, we reject it. We have our own investigation services."
Malik's statement coincided with widening concerns over more attacks likely to come in the coming days, as Pakistan's government steps up its attacks on Taliban hideouts along the Afghan border.
On Tuesday, Pakistan President Asif Ali Zardari is due to meet with U.S. President George Bush on the sidelines of the U.N. General Assembly in New York, with the war on terror likely to be their main focus of discussion.
Western diplomats in Islamabad said Saturday's attack was likely to intensify pressure on Zardari to oversee a tough new effort to curb the activities of Islamic militants.
The Taliban movement which is at the center of suspicions for backing Saturday's attack is led by Baitullah Mehsud, a militant commander who has forged close links to Osama bin Laden's Al Qaeda movement.
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.
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 said the main building could still collapse.
Khalid Hussain Abbasi, a rescue official, confirmed that six new bodies had been found, but would not say if any belonged to 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.
At least one American also died in the attack, according to the U.S. State Department. 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 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.
Witnesses and officials said the dump truck exploded about 60 feet away from the hotel at two heavy metal barriers blocking the entrance. The explosion reverberated throughout Islamabad and shattered windows hundreds of yards away.
Interior Ministry chief Rehman Malik told The Associated Press it was unclear who was behind the attack. But authorities had received intelligence there might be militant activity linked to Zardari's address to Parliament and security had been tightened, he said.
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 Qaeda fighters using Pakistan as a training, recruiting and regrouping ground to aid the insurgency in Afghanistan.
U.S. President George W. 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 Qaeda 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.
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."
Pakistan's army chief, Gen. Ashfaq Parvez Kayani, joined the chorus of condemnation Sunday, calling the attack "heinous" and saying the army stands "with the nation in its resolve to defeat the forces of extremism and terrorism."
The army has staged offensives against insurgents in the nation's northwest that have drawn revenge attacks by Taliban militants.
The hotel stood in a plot surrounded by government buildings. 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.