Combatants on Friday held the Libyan town of Misratah, 150 kilometres (95 miles) east of Tripoli, but the situation was "catastrophic" and troops encircled the town, a witness said.
Osman, a 27-year-old Sudanese, left Misratah Thursday evening aboard a Libyan taxi. He arrived early Friday at the Tunisian border and went to the transit camp at Choucha where he was awaiting repatriation.
"The situation in Misrata is completely catastrophic. There have been clashes between revolutionaries and soldiers of (Libyan leader Moamer) Kadhafi since the end of February. There are dead and wounded in the streets," Osman said.
"At the beginning the soldiers held the town, but the insurgents succeeded in taking Misratah and driving Kadhafi's forces back. Now the revolutionaries control the city centre, and the troops are all round, with armoured vehicles," he added.
"Shops are closed, there is nobody in the streets, just the revolutionaries with weapons, and they fire on Libyan soldiers and on black people whom they take for mercenaries.
"I have got friends who are still there, but they are blocked at Misratah's dromedary market because they are black. They have to be freed, they need to be helped," he pleaded.
Government troops last week launched several assaults in an attempt to recapture control of Misratah.
At least 21 people, including a child, were killed and dozens wounded last Sunday, during clashes and bombing raids, according to a medical source.
The revolution in Libya, which followed popular uprisings in Tunisia and Egypt that led to the ouster of long-installed heads of state, has driven tens of thousands of people, mainly expatriate workers, across the border into Tunisia.