By Peter Graff
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, U.S. 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.
"We only have one choice: we will stay in our land dead or alive," Gaddafi said in a fiery audio address, adding that his supporters were flocking to his vast Bab al-Aziziya compound after it was hit several times by NATO air strikes.
"We are stronger than your missiles, stronger than your planes, and the voice of the Libyan people is louder than explosions," he said in his customary impassioned tone.
He said he was ready to unleash between 250,000 to 500,00 Libyans to swarm across the country to cleanse it from "armed gangs," a reference to rebels controlling eastern Libya.
About 150 Gaddafi supporters demonstrated in central Tripoli, firing AK-47s in the air and waving posters of him.
State television later showed images of what it said was a meeting between Gaddafi and tribal leaders on Tuesday. Gaddafi, wearing dark glasses and traditional robes, was greeting the leaders in a small room without windows.
BOMBING RAIDS
A British Defence official said several operations carried out by fighter aircraft had targeted Gaddafi's secret police headquarters and a military installation on Tripoli's outskirts.
The bases, he said, were "engaged in the brutal repression of the civilian population and therefore a legitimate focus for NATO action."
Obama said in Washington there was an "inexorable trend of the regime forces being pushed back, being incapacitated."
"I think it is just a matter of time before Gaddafi goes."
Gaddafi's troops and the rebels have been locked in stalemate for weeks, neither able to hold territory on a road between Ajdabiyah in the east, which Gaddafi's forces shelled on Monday, and the Gaddafi-held oil town of Brega further west.
Rebels control the east of Libya, the western city of Misrata and the range of mountains near the border with Tunisia. They have been unable to advance on the capital against Gaddafi's better-equipped forces, despite NATO air strikes.
Gaddafi forces pulled back to high ground outside Yafran, 100 km (60 miles) southwest of Tripoli and 95 km from the coast road that serves as the main link between Gaddafi-held territory and the outside world.
The rebels lifted a weeks-long siege of Yafran on Monday.
Moussa Ibrahim dismissed the gains, saying the rebels did "not present any threat to the Libyan nation."
Rebel commander Juma Ibrahim in Zintan told Reuters that Gaddafi's forces had massed on Tuesday in their biggest numbers in the area since the start of the conflict.
"Gaddafi's troops and vehicles (are) north of Kalaa (about 7 km east of Yafran) to prepare to stop the advance of rebels from Yafran and Zintan towards Tripoli," he said.
"This is the largest number of troops we have seen in the western mountains since the war's start," he said, adding that NATO planes flying overhead had not struck Gaddafi's troops.
Accounts from the mountains could not be independently verified because access for reporters is limited.
DIPLOMATIC CONTACT WITH REBELS
As bombing intensifies, world powers were making diplomatic overtures to the rebels, including Russia and China, despite misgivings about interference in Libya's sovereign affairs.
Mikhail Margelov, Special Representative for the President of Russia for Africa, told reporters in the rebel capital of Benghazi on Tuesday that Gaddafi can no longer represent Libya and that Russia was ready to help in any way possible.
"We highly believe that Gaddafi has lost his legitimacy after the first bullet shot against the Libyan people," he said.
In Beijing, the Chinese Foreign Ministry said an Egypt-based Chinese diplomat had visited Benghazi for talks with the rebel-led National Transitional Council, adding to signs that China too is courting the insurgents.
China has declined to take sides, but its moves reflect recognition that Gaddafi's days may be numbered, said Yin Gang, an Arab expert at the Chinese Academy of Social Sciences.
Libya's pro-Gaddafi Foreign Minister Abdelati Obeidi is visiting China as a "special envoy" for his government and will hold talks with his counterpart Yang Jiechi.
(Additional reporting by Sherine El Madany in Benghazi, Youssef Boudlal in Yafran, Joseph Nasr in Rabat, Sami Aboudi in Cairo, Brian Love in Paris, Tim Cocks in Tunis, Chris Buckley in Beijing, Stephanie Nebehay in Geneva, Matt Spetalnick and Laura MacInnis in Washington, Michael Holden in London and Steve Gutterman in Moscow; Writing by Tim Cocks and John Irish; Editing by Jon Hemming)