A group of migrants who spent nearly three weeks trapped onboard a merchant ship in torrid conditions face possible deportation to their home countries after they were finally allowed to disembark in Tunisia, aid groups have warned.

The 75 migrants, about half of whom are minors or unaccompanied children, were rescued on 31 May by the Maridive 601 only to spend the next 20 days at sea as European authorities refused to let them land.

“The migrant boat was ignored by Italian and Maltese authorities, though they were in distress in international waters”, said a spokesperson for Alarm Phone, a hotline service for migrants in distress at sea that was alerted to the ship’s plight by crew members. “This is a violation of international law and maritime conventions”.

The migrants were rescued from a small vessel by an Egyptian tugboat. Photograph: Courtesy of Forum Tunisien pour les Droits Economiques et Sociaux

Heat and humidity onboard the Maridive 501, an Egyptian tugboat that services offshore oil platforms, were insufferable, said aid groups. Food and water were scarce, scabies broke out and spread, and several people suffered fractures and other injuries during the rescue operation.

Witnesses said the psychological strain was immense for migrants and crew members alike.

The brother of one Bangladeshi man said on 3 June: “Today is Eid [the festival marking the end of Ramadan]. But the day is not for me. My brother is on the ship. I can’t take it any more. How is he? How can I explain my feelings to you? When I get good news, this will be my Eid gift and that day will be my Eid day.”

Six days later, he said: “How many days will they stay there? Who can take care of him? I am depressed, every day my mother is crying.”

The ship’s captain, Faouz Samir, asked repeatedly to be allowed to land at the nearest port, in Zarzis, but was initially refused permission. Regional authorities said migrant centres in Medenine were too overcrowded.

On 6 June, the migrants staged an onboard protest, asking to be sent to Europe. Video of the protest was published by the Forum Tunisien pour les Droits Economiques et Sociaux.

The closure of Italian and Maltese ports to rescue ships has seemingly had a ripple effect, with Tunisia closing its own harbours to rescued people in order to avoid an overwhelming influx of migrants.

Conditions onboard the Maridive 601 were insufferable, with little food and water, said aid groups. Photograph: Courtesy of Forum Tunisien pour les Droits Economiques et Sociaux

On Tuesday evening, however, the Tunisian authorities relented. The migrants, who are mainly from Bangladeshi but also include Egyptians, Moroccans and Sudanese, will now be transferred to a detention centre.

Aid groups, however, who had been demanding an immediate disembarkation in view of the medical emergency onboard, are concerned people may be sent back to Libya or even deported to their home countries after landing in the port of Zarzis. The governor of Medenine had previously said the boat would be allowed to dock only if all the migrants were immediately deported.

“We are happy for the survivors. They are exhausted, some are traumatised, but we will accompany them so that we can finally find respite and reflect on the different alternatives available to them,” said Wajdi Ben Mhamed, head of the International Organisation for Migration’s Zarzis office.

The IOM said its protection team would assist the survivors with “their protection needs and provide, for those who have requested it, assistance for voluntary return to their country of origin’’.

Relatives claim some of the Bangladeshi survivors were told that food, water and medical treatment would be withheld if they did not accept deportation.

One man who spoke to his brother on 18 June said fears of imminent deportation had been exacerbated by the visit of a Bangladeshi envoy to the boat. The envoy’s visit followed a meeting five days earlier with the Tunisian minister of the interior.

Another relative said of a Bangladeshi migrant aboard the tugboat: “In Bangladesh there are people who want to kill him. He paid all the money and went to Libya to get away from the problems in Bangladesh. Then he escaped from Libya because of the problems there. He wants to go to Europe.”

Médecins Sans Frontières warned that Tunisia could not be defined a safe haven for migrants and refugees, given that it had no functioning asylum system in place. “The nearest places of safety for rescues in the central Mediterranean are Italy or Malta,” said a spokesperson.

The boat was finally allowed to disembark in Tunisia, but the migrants may now face deportation. Photograph: Courtesy of Forum Tunisien pour les Droits Economiques et Sociaux

A dangerous precedent would be set if an agreement was found to deport those rescued to their countries of origin quickly after disembarkation in Tunisia. Aid groups warn that boats like the Maridive would turn into migrant holding facilities until deportations were arranged. Many more boats could thus turn from places of rescue to prison islands, floating along north African shores.

Giorgia Linardi, of SeaWatch in Italy said: “After this episode we should reflect on whether Tunisia qualifies as a place of safety, as our sources suggested that the migrants could be immediately repatriated or expelled from the country. The situation aboard the Maridive is very much confronted with the situation faced right now by the SeaWatch vessel with 53 migrants on board which is still floating in front of Italian territorial waters. As of now, the attitude of the Italian authorities is no different from the attitude of the Tunisian authorities towards the Maridive despite the two states having a different framework in terms of protection of human rights and in terms of asylum system in place.”

With sea conditions currently favourable, thousands are preparing to leave Libya, where war and political instability have been aggravated by floods caused by heavy rain.

Without rescue boats, however, the number of shipwrecks is likely to rise further. Only two of the 10 NGO rescue boats that were active in the Mediterranean are still present.

According to data from the UN and the IOM, about 3,200 people have reached Italy and Malta from North Africa since the beginning of 2019, and almost 350 have died en route – putting the death rate for those crossing at about 11% along the central Mediterranean route.