* District has been flashpoint of anti-Gaddafi protests * Graffiti mimic slogans in Egypt and Tunisia
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TRIPOLI, Feb 28 (Reuters) - Security forces fired in the air as hundreds of demonstrators gathered to protest against Libyan leader Muammar Gaddafi in a district of the capital Tripoli on Monday.
The protest took place in the Tajoura neighbourhood, flashpoint of anti-Gaddafi protests in eastern Tripoli, where residents had previously reported clashes between Gaddafi opponents and forces loyal to him.
About 400 protesters shouted anti-Gaddafi slogans and displayed the green, black and red flag which has been adopted as the symbol of rebellion against his four-decade rule.
As the protest unfolded, two sport utility vehicles pulled into the area where the protest was taking place.
The occupants, wearing green bandanas, the colour of Libya's national flag, jumped out of their vehicles in a nearby street and fired into the air.
Three police vans and several pickup trucks full of armed men were parked at the opposite end of a street leading to the roundabout where the protest was taking place.
Graffiti on one wall said "Gaddafi game over," mimicking slogans used in protests that toppled the leaders of Egypt and Tunisia.
A military helicopter was flying overhead and vehicles of the security forces were seen driving around the area.
Two residents said separately that four protesters had been killed while attending a similar rally late on Sunday. They said Gaddafi militiamen arrived in the area in SUVs and opened fire.
"Gaddafi militia were shooting randomly. They arrived in four cars. Four people were killed. There was a funeral today," said a computer engineer who gave his name only as Mohammed.
BUCKETS OF PAINT
Residents said groups of people appeared in the neighbourhood earlier in the day to paint over anti-Gaddafi graffiti.
Empty buckets of paint were still scattered around the roundabout as protesters doggedly sprayed new anti-government slogans on the freshly painted walls.
The atmosphere was nervous and protesters were stopping cars driving past to check for any weapons.
In one incident, an argument broke out, prompting one man to slash the tyres of a car with a knife. They car drove off swiftly, its flat tyres screeching against the asphalt.
Residents said armed men stormed into a local clinic several days ago and fired inside it indiscriminately.
"They shot, they shot," said one man, as he pointed at numerous bullet marks on the walls and windows inside the deserted clinic. He said no one was hurt in the incident.
Omar, a doctor, said: "They shot inside the clinic. One bullet passed just above my head." Like other protesters, he asked not to use his full name for fear of being indentified by the government.
The government denies using deliberate force against civilians. A government spokesman said on Monday troops might have fired before but it was because they were not properly trained.
Earlier, Tajoura residents said several people wounded in recent clashed had disappeared from state hospitals, forcing them to treat any new wounded people in smaller, locally run neighbourhood clinics.
The number of casualties in Tripoli from recent clashes could not be independently verified.
The protest was still going when a Reuters reporter left the scene. The reporter was in Tripoli as part of a tour for foreign media organised by the government. (Editing by Andrew Dobbie)