TRIPOLI (Reuters) – NATO warplanes struck the Libyan capital several times an hour, hour after hour on Tuesday in the most sustained bombardment of Tripoli since the bombing campaign began, but Muammar Gaddafi said he would fight to the death.

As a grey pall of smoke from the air strikes hung over the Tripoli skyline, President Barack Obama said it was only a matter of time till the Libyan leader was gone.

At least 31 people were killed in 60 strikes on the Libyan capital in the raids, government spokesman Moussa Ibrahim told reporters. His account could not be independently verified.

Describing planes flying overhead and explosions around him, Gaddafi was defiant.