"The sophistication of the blast shows it's the work of al Qaeda," a Pakistani intelligence officer told Reuters.

Teams combing the burnt shell of the hotel found more charred bodies after the blast on Saturday evening ignited a blaze that swept through the hotel, part of a US-based chain and a favorite haunt of diplomats and wealthy Pakistanis.

Four foreigners were killed including the Czech ambassador, his Vietnamese partner and two members of the US armed forces assigned to the US embassy. Denmark's security service said one of their staff, attached to the Danish mission in the capital, was missing, presumed dead. An American State Department employee was also missing, a spokesman said.

The Interior Ministry said 266 people were wounded, 11 of them foreigners, after the bomber blew up a truck packed with 600 kg (1,320 lb) of explosives including artillery shells, mortar bombs and shrapnel.

Internal security in Pakistan has deteriorated alarmingly over the past two years.