Libyan security forces violently attacked a protest by refugees in front of a UN community centre in Tripoli on Monday, triggering widespread condemnation.
Activists and migrants said armed security personnel attacked the refugees and asylum seekers, arresting hundreds.
The Norwegian Refugee Council (NRC) and the International Rescue Committee (IRC), two humanitarian agencies, said more than 600 migrants were detained in the raid. They called on the authorities to release them immediately.
Those arrested were sent to a detention centre in the nearby town of Ain Zara. Others managed to flee, activist Tarik Lamloum told the AP news agency.
A government spokesperson did not immediately reply to requests for comment.
In a joint statement with the IRC sent to The Independent, the NRC said the centre provided humanitarian assistance to refugees and asylum seekers before it was permanently closed in December.
“We are alarmed by the detention of hundreds of migrants, refugees and asylum seekers, including women and children, that were camped out in front of the former Community Day Centre in Tripoli,” said Dax Roque, the NRC’s Libya country director.
“Witnesses have told us they were met with violence this morning and that makeshift tents were burnt down.”
In October, the Libyan authorities rounded up more than 5,000 migrants, including hundreds of children and women, many pregnant, according to the UN. Authorities at the time described it as a security operation against illegal migration and drug trafficking.
Mr Roque added: “Since the mass detention of thousands of migrants, refugees, and asylum seekers in October of last year, the situation for this population in Libya has only got worse.”
Libya has been in constant turmoil since an uprising toppled and killed long-time dictator Muammar Gaddafi in 2011. Libya has since become the main transit point for migrants seeking to cross the Mediterranean to Europe.
Traffickers pack ill-equipped rubber or wooden boats with desperate migrants, many fleeing war or poverty in Africa and the Middle East. But thousands have drowned during the dangerous journey, and those rescued and returned to Libya are often taken to overcrowded and inhumane detention camps that are rife with torture, sexual assault and other abuses.
Mr Lamloum said at least one migrant community leader was shot during the raid.
In the joint statement, Thomas Garofalo, the IRC’s Libya director, said: “Our medical teams have been supporting those injured during this morning’s arrests, including one person suffering from a gunshot wound.
“As we enter a new year, the events unfolding should act as yet another reminder that the current situation for migrants and refugees in Libya is untenable and requires a new approach that respects the rights of people on the move.”