Dramatic footage of Saturday night's attack showed the carnage could have been far worse, but the attacker failed to get through a secondary barrier when he crashed his explosives-laden truck into the hotel's security gates.

The interior ministry said the truck was packed with 600 kilos (1,300 pounds) of explosives, and pointed a finger at Taliban militants allied with Al-Qaeda who are based in the remote areas along the border with Afghanistan.

"All roads lead to Fata," ministry official Rehman Mailk told a news conference, using the acronym for the rugged tribal areas that have become a safe-haven for militants despite an army campaign to root them out.

"It has the hallmarks of Al-Qaeda," a senior official involved in the investigation told AFP. "It was an Al-Qaeda style bombing."

Several security officials said at least 60 people were killed in the carnage . Malik put the number confirmed so far at 53 dead and 266 injured.

Rescuers were continuing to pick through the rubble of the hotel, which was all but destroyed in the massive blast -- heard for miles around -- and a subsequent fire that swept through the 300-room hotel.

Some bodies pulled from the debris were burnt beyond recognition.

Czech ambassador Ivo Zdarek, who was living at the hotel, was among the dead.

The brazen attack appeared to have been timed to inflict maximum casualties , ripping through the hotel when it was packed with families having dinner to break the daily fast in the Muslim holy month of Ramadan.

The bombing came on the one-year anniversary of Osama bin Laden's call for Pakistani Muslims to unleash jihad or holy war against the government, a vital ally in the US-led "war on terror".

Closed-circuit footage showed that the attacker rammed his truck into the gates but failed to get through a second barrier which is raised again after each vehicle enters the heavily secured complex.

Malik said the attacker intended to drive right into the lobby of the luxury hotel . He apparently tried to convince the guards to lower the second barrier -- and when they would not, he blew himself up in the truck's cabin.

The guards then tried to put out the fire in the truck, and it was several minutes before the second larger blast devastated the Marriott, which was popular with politicians, foreigners and the Pakistani elite.

No group has yet claimed responsibility.

But the bombing is a serious challenge to new President Asif Ali Zardari, who faces a desperate battle against Al-Qaeda and Taliban militants whose campaign of violence has killed 1,300 people in Pakistan this year.

"We will rid the country of this cancer," Zardari, who took office less than two weeks ago, said in a message to the nation after the attack. "I appeal to all democratic forces to come and save Pakistan."

Analysts say the ability to carry out such a massive bombing at one of the most secure sites in the capital, not far from parliament and the prime minister's residence, is an unmistakable sign of the militants' reach.

Zardari's predecessor Pervez Musharraf turned Pakistan into a close ally of the United States after the September 11 attacks in 2001, and the government has waged a crackdown on militants in Pakistan's volatile northwest.

That campaign has drawn the ire of many in Pakistan, the world's only nuclear-armed Islamic nation, and critics say elements of the army and intelligence services are supporting the militants.

Many militants poured into the northwest tribal areas from across the border in Afghanistan when the United States invaded after 9/11, and much of the region is now effectively outside the Pakistani army's control.

The administration of US President George W. Bush says militants are using the area as a base of operations to lead the deadly insurgency in Afghanistan, and US forces have fired missiles and even raided the region.

But even Zardari has warned that US operations on Pakistani soil are unacceptable. The perceived violation of sovereignty, and the Pakistan army's campaign against militants, have infuriated many Pakistanis.

Exactly one year ago on September 20, Bin Laden called on Muslims in Pakistan "to carry out jihad and fighting to remove (Musharraf), his government, his army and those who help him."

Zardari left Sunday for New York, where he will meet Bush for the first time since taking over the presidency. Bush, along with leaders from around the world, denounced the latest bombing.

"This attack is a reminder of the ongoing threat faced by Pakistan, the United States and all those who stand against violent extremism," he said.