Selective and partial disembarkation "cannot be considered legal under maritime law conventions," says Doctors Without Borders.
Italy has been preventing some irregular migrants who were rescued at sea from disembarking in the country, which global non-governmental organisations say is against international law.
Late on Sunday, Italian officials allowed only 357 of 572 irregular migrants on board a rescue boat to disembark, local media reported.
The ship Geo Barents, which had rescued migrants in recent weeks through its operations in the Mediterranean Sea and waited for days in the open sea for Italy to designate a safe harbour for their evacuation, was allowed to arrive in the port of Catania on Sunday evening.
Under a decree recently adopted by the right-wing coalition government led by Giorgia Meloni, not all of the 572 migrants on board were allowed to disembark.
According to local media, Italian authorities boarded the ship and evaluated the health of the migrants one by one and gave the green light to the disembarkation of only 357 of them who were considered vulnerable, while the other 215 remained on the ship.
Doctors Without Borders (MSF), which operates the ship, said in a statement that a rescue operation can only be considered complete when everyone is evacuated to safety.
It added that “selective and partial disembarkation, as proposed by the Italian authorities, cannot be considered legal under maritime law conventions.”
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SOS Humanity to take legal action
Earlier on Sunday, Italy allowed a German-flagged rescue ship to enter a port in Sicily and disembark women, children and ill migrants.
Humanity-1, operated by German charity SOS Humanity, entered the port of Catania escorted by an Italian coast guard boat.
In line with the latest decree on irregular migration issued by the government, Italian authorities carried out health checks on the 179 migrants on board, and 35 who were said to be adult men without medical problems were not allowed to disembark.
“On Monday, SOS Humanity takes legal action against the decree of the Italian government & the prevention of the disembarkation of 35 rescued people from the #Humanity1! Italy's actions violate European law & the Geneva Refugee Convention,” the NGO said on Twitter.
The region of the Mediterranean between Italy, Malta and Libya has come to the fore in recent years as one of the irregular migration routes frequently used in the transition from Africa to Europe.
Instead of European states, European NGOs usually rescue irregular migrants who call for help at sea.
These NGOs have difficulties in evacuating the migrants they rescue from time to time due to European states' failure to provide a "safe haven."
Migrants who can cross the Mediterranean or are rescued usually end up in Italy, where they first set foot in Europe.
Every year, many irregular migrants die while trying to cross the Mediterranean due to their boat capsizing or a lack of water due to overcrowding on the boats.
READ MORE: Why the UN slammed Italy for failing to save 200 migrants from drowning