Authorities in eastern and western Libya have intensified a crackdown on migrants and refugees in the last month with mass arrests, detentions and expulsions, Amnesty International said on Tuesday, accusing the EU of complicity in abuse.

Libya, where control is split between rival western and eastern factions, has been a major transit route for people fleeing conflict and poverty towards Europe by the dangerous sea route since a 2011 NATO-backed uprising toppled Muammar Gaddafi.

The EU and its member states have long supported and trained the Libyan coastguard, which intercepts migrants at sea. While the EU formally recognises only the Tripoli-based government, since last year it has also stepped up engagement with the rival authorities in the east.

Amnesty said the crackdown included mass arrests across multiple cities, forced evictions and expulsion of hundreds of migrants, including nationals of war-torn Sudan, without the chance to ask for asylum or challenge their deportation.

“The EU has long bankrolled migration control in Libya with its support to the Libyan Coast Guard, which has already made it complicit in horrific violations and abuses," said Diana Elahawy, Amnesty International’s deputy regional director for the Middle East and North Africa.

"Extending this cooperation to eastern-based armed groups with records of committing war crimes and other abuses with impunity shows a shocking disregard, not only for international law, but also for human life and dignity,” Elahawy added.

The EU's executive European Commission, the Libyan government in Tripoli and the administration in the east did not immediately respond to requests for comment. EU officials have defended their cooperation with Libya as helping to save lives at sea and curb unlawful trafficking.

In a letter to EU leaders last week, Commission President Ursula von der Leyen said “continued EU engagement with Libya remains indispensable,” citing a rise in irregular crossings, towards Greece via the Eastern Mediterranean route.

“We are providing targeted financial and operational support to strengthen border management, search-and-rescue and anti-smuggling capacities, and reduce illegal departures and the loss of lives at sea,” von der Leyen said.

Last summer, EU Migration Commissioner Magnus Brunner travelled to eastern Libya for talks with authorities there but was expelled shortly after arrival.