For hundreds of black African migrant workers squatting in makeshift shelters on the outskirts of Tripoli, Libya's revolution has brought not hope and freedom but fear, hunger and increasing desperation.

At the abandoned fishing port at Sidi Bilal, about 25km from the centre of the capital, more than 600 migrant workers are living in squalor, hanging blankets from dilapidated boats to block out the sun, boiling scant portions of rice over open fires and waiting for rare deliveries of aid.

Lured to the Libya of Muammar Gaddafi to seek work, with his ousting they now find themselves not only jobless but facing arrest, attacks and robberies because of accusations that black African mercenaries supported the Gaddafi regime.

Western governments and human rights groups have raised concerns about the stigmatising of black African migrants and warned that their treatment will be a key test of the new government's democratic credentials.

For those baking in the sun in Sidi Bilal, it is a test the new regime is failing badly.

"We came here to work, to do the jobs the Libyans would not do.

"Now they hate us and attack us," said Bright Adams, a 33-year-old Nigerian at the camp who had been working as a labourer in Tripoli since 2008.

"We are barely surviving here. There is no food, no drinking water and no safety. We need help," he said.

Most of the migrants fled to the camp late last month, when rebel fighters controlled by Libya's National Transitional Council seized control of Tripoli.

In a report earlier this month, New York's Human Rights Watch said the council's forces had carried out mass arrests of migrant workers in Tripoli and were holding them in makeshift detention centres throughout the capital.

Saying, "It's a dangerous time to be dark-skinned in Tripoli", the report alleged widespread persecution of black Africans, up to 2million of whom had been working in Libya prior to the uprising, based solely on the colour of their skin.

Last week, a UN team said it was concerned about the reports of mass arrests of "black Africans who are suspected of being pro-Gaddafi mercenaries".

Migrant workers at Sidi Bilal said National Transitional Council fighters had raided their homes, seized their passports and local identification papers and robbed them of all their belongings.