Six Britons and an unknown number of Saudi, German, Moroccan, Afghan and US citizens, were among those hurt.
Funerals of those killed have begun to be held in Islamabad. However, there are fears that more bodies will be found as rescue teams move deeper into the hotel.
There has been no claim of responsibility so far, but the interior ministry said the attackers were linked to Islamist militants in the north-west border region near Afghanistan.
The heavily-guarded hotel was attacked at about 2000 (1500 GMT) on Saturday, when a lorry blew up at the hotel entrance after it was stopped for a security check.
President Asif Ali Zardari vows to rid Pakistan of Islamic militants
The interior ministry has shown a security video of the moments before the blast.
A six-wheeler lorry rams the security barrier at the hotel gate. Shots are fired and the vehicle starts to burn. The guards run then return to try to douse the flames.
There is no footage of the main blast because it destroyed the camera, but officials said the vehicle was packed with 600kg of high quality explosives as well as grenades and mortars.
Aluminium powder was also used to accelerate the explosion and added to the ferocity of the blaze, officials said.
"I do not believe this is a breakdown in security. The attackers had disguised the truck well as it was covered with a tarpaulin and loaded with bricks and gravel," said interior ministry adviser, Ramen Malik.
The force of the explosion created a crater about 8m (27ft) deep, and triggered a fire which engulfed the 290-room, five-storey building for hours.
Witnesses described a scene of horror as blood-covered victims were pulled from the wreckage and guests and staff ran for cover from shattered glass and flames.
The fire has now burned out and rescue workers have been searching the building room-by-room, pulling bodies out of the blackened debris.
Officials have warned that the building could collapse.
The attack came just hours after President Asif Ali Zardari vowed to fight terrorism, in his first speech to parliament since his election earlier this month.
After the bombing, he addressed the nation on television.
"This is an epidemic, a cancer in Pakistan which we will root out," he said. "We will not be afraid of these cowards."
Mr Zardari stopped in London on his way to New York to attend the UN General Assembly session, where he will meet President George W Bush on the sidelines of the conference.
The meeting comes amid tension between the two countries over US cross-border military attacks on militants in tribal areas of Pakistan, close to the Afghan border.
In the wake of the attack, President Bush pledged assistance to Pakistan in "confronting this threat and bringing the perpetrators to justice".
He said it was "a reminder of the ongoing threat faced by Pakistan, the United States, and all those who stand against violent extremism".
The Marriott is the most prestigious hotel in the capital, and is located near government buildings and diplomatic missions. It is popular with foreigners and the Pakistani elite.
As a precaution, British Airways said it was cancelling two flights to Pakistan on Sunday and Tuesday. A spokesman told the BBC a decision would be taken later about flights from Wednesday onwards.
The Marriott has previously been the target of militants. Last year a suicide bomber killed himself and one other in an attack at the hotel.
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