Fire broke out at the Marriott Hotel in the Pakistani capital, Islamabad, on Thursday, five months after a suicide truck bomber killed 55 people there.
There were no reports of any deaths in the blaze but a doctor at a city hospital said 12 to 15 people had been injured.
"They have burn injuries. We are treating them," said the doctor, Mohammad Farooq.
Thicks smoke rose over the hotel and flames could be seen on the ground and first floors, a witness said.
Islamabad's top administrator Kamran Lashari told Reuters the fire was apparently caused by an electrical short-circuit.
The hotel reopened in late December, just over three months after the Sept. 20 bomb attack blamed on Islamist militants.
The blast sparked a fire that gutted the building, one of two top hotels in the capital and long a favourite haunt of diplomats and well-heeled Pakistanis.