Doctors Without Borders has said that it is temporarily suspending the activity of its rescue ship owing to alleged threats from Libya. The Libyan coastguard has increasingly become more aggressive in patrolling the waters off its coasts where human traffickers launch boats crowded with migrants desperate to reach Europe.

The humanitarian group said the rescue coordination centre operated by Italy’s coastguard had informed it on Friday that the Libyan threats pose a security risk. The group added that Libyan authorities declared their own rescue area, extending into international waters, the same day.

Doctors Without Borders said its medical crew will keep working from a ship operated by another aid group while its own vessel, Vos Prudence, is not involved in migrant rescues.

The Italian government agreed last month to dispatch a naval mission to assist the Libyan coastguard with anti-smuggler patrols. Hundreds of thousands of rescued asylum-seekers, many of them fleeing poverty in Africa, have been brought to safety in Italian ports in recent years.

The government has pressured rescue groups to agree to rules that would forbid them entering Libyan waters to save migrants without specific authorisation and to agree that armed Italian judicial authorities may board their ships. Italy is telling rescue organisations to subscribe to the rules or risk not being allowed to dock in Italian ports.

Doctors Without Borders has refused to endorse the rules, while other humanitarian groups have given their approval.

Critics of the new policy said it could put lives at risk by delaying rescues in Libyan waters. They also contend that if the Libyan coastguard blocks smugglers’ boats, migrants will be returned to inhumane conditions, including beatings and forced labour, in Libyan detention centres.

“If humanitarian ships are pushed out of the Mediterranean, there will be fewer ships ready to aid persons before they drown,” said the president of Doctors Without Borders Italy, Loris De Filippi, in a statement. “And whoever doesn’t drown will be intercepted and brought back to Libya, which we know to be a place of absent legality, arbitrary detention and extreme violence.”

A Spanish humanitarian group, Proactiva Open Arms, said the Libyan coastguard ordered its rescue ship to move north and fired warning shots last week when the vessel was involved in search-and-rescue work outside Libyan waters.

Humanitarian groups have had ships monitoring the Mediterranean outside Libya’s territorial waters to help rescue migrants from smugglers’ boats in distress. The Italian coastguard coordinates the rescues, including those conducted by naval vessels from other European countries.