By Maria Golovnina
TRIPOLI (Reuters) - Sustained gunfire rang out near Libyan leader Muammar Gaddafi's heavily fortified compound in Tripoli on Friday and residents said they saw snipers on rooftops and pools of blood on the streets.
It was not clear what triggered long bursts of machinegun and automatic gunfire that echoed around the city center for about 20 minutes and stopped before dawn.
Cars were heard speeding along central Tripoli streets, their tires screeching against the asphalt. Distant shouting or chanting was also heard.
"There were pools of blood on the streets. You will not find anything now. It's been hosed down and cleaned by the fire trucks," said one Tripoli resident.
Gunfire is often heard in Tripoli where people like to shoot their weapons into the air in celebration or defiance, but Friday's episode was different and sounded like a gunfight, witnesses said.
Witness accounts could not be independently verified because journalists in Tripoli are not allowed to report freely and were prevented from leaving their hotel on Friday.
State forces have cracked down on all forms of dissent in Tripoli since the start of an anti-Gaddafi uprising in February.
But the city has been on edge in past days, with people's anxiety compounded by fuel shortages and increasingly long queues outside bakeries and gas stations.
With Gaddafi's air defenses crippled by Western air strikes, cracks in his hold on power have also started to emerge this week with the defection of a key minister to Britain.
A Libyan man who lives in exile abroad and maintains daily contact with relatives in Tripoli, said sustained gunfire was also heard in the working class suburb of Tajoura before dawn.
"The Libyan army has put a lot of snipers on the roofs of schools near mosques. People are afraid, they are staying at home," he said.
Mosques in places like Tajoura have been the focus of anti-Gaddafi protests in the past. Militiamen have cracked down on them violently, local residents say.
"Many people, young men, have been arrested. Two of my cousins have been arrested," said the exiled man who asked not to be named. "They are arresting people who have taken part in earlier protests, or just young people."
He said militiamen seeking to prevent a protest had blocked worshippers from entering a central mosque in Tajoura earlier on Friday. No one was hurt in the confrontation, he said.
Security has been tight around Tripoli, and new army checkpoints have sprung up in the city center where many streets are adorned with large portraits of Gaddafi.
The roar of jet engines has been regularly heard in the skies above Tripoli as Western forces continue to enforce a U.N.-authorized no fly zone over Libya.
(Writing by Maria Golovnina; editing by Ralph Boulton)