* Down from 24,000 to 2,000 a day
* Roadblocks, holding camp said set up in Libya
GENEVA, March 7 (Reuters) -- Flows of refugees from western Libya dropped dramatically over the weekend, possibly because government forces have set up road blocs and a holding camp to stop people leaving, international aid chiefs said on Monday.
They told a news conference that whereas 24,000 had been crossing daily a week ago into Tunisia, this had dropped to around 2,000 a day over the weekend.
"We don't know the reason, because we know there are many tens of thousands more who want to get out. But we can make our guesses," said William Lacy Spring, Director-General of the Geneva-based International Organisation for Migration (IOM).
Antonio Guterres, U.N. High Commissioner for Refugees, said the slowdown began when Libyan forces of the government of Muammar Gaddafi moved into border areas two days ago. "Until then the border had been uncontrolled," he said.
Valerie Amos, United Nations Emergency Relief Coordinator, who spoke to refugees who had entered Tunisia at the weekend, said they had told her of road blocks set up by the Gaddafi forces between the capital Tripoli and the frontier.
"Some people told me a camp had been set up about 17 kilometres (10 miles) inside Libya by the government forces and that many people were being held there," she said. "But the U.N. has not been able to obtain any more information on that."
Separately, a Swiss-based Libyan exile group said Gaddafi forces were working to move all foreigners including migrant workers from areas under their control to a small port near the town of Misrata, west of Tripoli.
The foreigners are "to be deported to Italy by boat", the press service of the Libyan Human Rights Solidarity group said. There was no way of checking the report, although over the past two weeks the group has proven to have good sources in Libya. (Reporting by Robert Evans; Editing by Jonathan Lynn and Ralph Boulton)