Rome - The situation has worsened on board a migrant rescue ship operated by German activists in the Mediterranean, with close quarters and bad weather conditions leading to severe seasickness and flashbacks for those with post-traumatic stress disorder.

A storm at sea is now returning, and the ship's passengers and crew need a safe harbour, Berlin's Sea-Watch NGO tweeted on Wednesday.

"We do not have the capacity or the rescourses [sic] to sustain this situation for much longer," Sea-Watch 3's medical team wrote in an "urgent request" dated Tuesday.

Dire situation

The Sea-Watch 3 vessel rescued 32 people in distress at sea off the coast of Libya on December 22 and has since been blocked from docking in Italy or Malta. The migrants rescued include four women and seven children, four of whom are unaccompanied.

The storm has forced the ship's crew to pack the migrants together in a small area below deck.

EU states have been at loggerheads on the migration issue, with countries disagreeing over who should assume responsibility for migrants saved at sea. Another vessel, also run by a German NGO, is awaiting permission to dock.

Malta refuses more migrants

Sea-Eye's Professor Albrecht Penck vessel saved another 17 people in the central Mediterranean on December 29. Both its ship and the Sea-Watch 3 are located just off Malta.

The country defended its refusal to take in the migrants on Wednesday. In a tweet, Maltese Home Affairs Minister Michael Farrugia provided a map of the area off Libya where the NGO boats carried out their rescues.

"Malta was neither the appropriate nor the competent [search and rescue] authority," he said.

Ongoing negotiations

His tweet came shortly after the Dutch government said it was prepared to take in some of the migrants - but only on the condition that other EU countries do the same.

"Negotiations coordinated by the European Commission are under way between the different European countries," Dutch security and justice ministry spokesman Lennart Wegewijs told AFP.

Malta and Italy have borne the brunt of sea migration for years.

On Monday, two boats packed with a total of 180 migrants were rescued off Malta and taken to the country.

But the two countries have closed their ports to NGO vessels in a bid to dissuade migrants from trying to reach Europe by setting sail from Africa.