The hotel blast caused a severe natural gas leak that set the top floor of the five-story, 258-room hotel on fire, police said.
The explosion was heard 15 kilometres away.
The blaze that followed quickly engulfed the entire structure of the Marriott hotel.
About two-thirds of the building caught fire as a result of the explosion after a natural gas pipe was blown open, and the reception area was completely destroyed.

The owner of the Marriott Hotel, Hashoo Group, owned by Sadruddin Hashwani, said the truck carrying the bomb had been stopped at the front barrier. "
Some shots were fired.
One of our guards fired back, and in the meantime the suicide bomber detonated all the explosives.
All the guards on the gate died", said Hashwani.
The hotel blast caused a severe natural gas leak that set the top floor of the five-story, 258-room hotel on fire, police said. The explosion was heard 15 kilometres away. The blaze that followed quickly engulfed the entire structure of the Marriott hotel. About two-thirds of the building caught fire as a result of the explosion after a natural gas pipe was blown open, and the reception area was completely destroyed.
The owner of the Marriott Hotel, Hashoo Group, owned by Sadruddin Hashwani, said the truck carrying the bomb had been stopped at the front barrier. "Some shots were fired. One of our guards fired back, and in the meantime the suicide bomber detonated all the explosives. All the guards on the gate died", said Hashwani.
Islamabad Marriott Hotel bombing