Italy's new Interior Minister Matteo Piantedosi has defended his country's migrant policy following widespread criticism over a decision to allow only the most vulnerable to disembark from charity rescue ships.

On Monday, Piantedosi insisted that Italy was treating migrants "with humanity."

Around 500 migrants disembarked in the Sicilian port of Catania over the weekend after being rescued by two charity ships from leaky, overcrowded boats seeking to cross from North Africa to Europe.

But around 250 from the two ships were denied permission to land under orders of Italy's new hard-right government, including a group of 35 men onboard the German-flagged Humanity 1, a vessel then ordered to leave.

Nongovernmental organizations (NGOs) said the move to select who could disembark was illegal and warned of desperate conditions onboard the two ships, which remain in the port.

Three men on Monday jumped from one of them, the Geo Barents, run by Doctors Without Borders (MSF), before being swiftly picked up out of the water, the charity said.

Afterward, a dozen other migrants stood on the deck of the ship chanting "Help us," an Agence France-Presse (AFP) reporter witnessed.

"We are behaving with humanity but firmly based on our principles," said Piantedosi, on the sidelines of an event in Rome.

He said migrants on other ships had been welcomed into Italian ports, and those left on board were being "constantly monitored by the competent authorities."

Authorities in Syracuse confirmed to AFP on Monday that more than 500 people found in distress off Malta had been rescued by Italian authorities and disembarked in Sicily.

Piantedosi said he was working at a national and European level to resolve the issue, after years of complaints from Rome that the EU was not doing enough.

Italy's new government, led by Prime Minister Giorgia Meloni's far-right Brothers of Italy party, has vowed to stop the tens of thousands of migrants who arrive on the country's shores each year.

One of her deputy prime ministers, League leader Matteo Salvini, is currently on trial for blocking migrant boats when he was interior minister in 2019.

He said Monday the arrivals must be stopped, tweeting: "They are organized trips, increasingly dangerous, which finance weapons and drugs. They must be cut off."

'Healthy men'

After days at sea, Geo Barents was given permission to disembark 357 people, including children, while the authorities refused entry to 215 others.

Nearby, Humanity 1 disembarked 144 people, but 35 adult male migrants onboard were refused.

A government decree issued Friday said Humanity 1 was only allowed into an Italian port for the time it took to help those in "emergency conditions."

The charity SOS Humanity, which operates the ship, said authorities decided after a "brief" medical exam that the 35 men were "healthy" and so need not disembark.

But it said no translator attended and there was no psychological evaluation and has launched legal action against the government for selecting who can disembark.

"If a port is secure, then it's secure for everybody," SOS Humanity lawyer Riccardo Campochiaro told AFP.

International obligations

UN agencies the UNHCR, the U.N. Refugee Agency and the International Organization for Migration all urged the disembarkation of the migrants "without delay."

In a joint statement Monday, they welcomed Italy's moves to let off many of the migrants but said, "a solution is urgently needed for all remaining survivors."

They referred also to two other rescue ships, the Ocean Viking and Rise Above, which have been waiting off Sicily with around 230 and 90 migrants respectively.

Media reports late Monday said Rise Above had been assigned a port in southern Italy.

A group of civil society organizations, including ActionAid International, Human Rights Watch and the Norwegian Refugee Council, echoed the call for rapid disembarkation.

Amnesty International has accused Italy of "violating its international obligations," saying "the law of the sea is clear; a rescue ends when all those rescued are disembarked in a place of safety."

Psychological stress

One of those left onboard Geo Barents was later evacuated by ambulance after suffering "acute abdominal pain", MSF said on Monday, bringing the total remaining to 214.

Antonio Nicita, a senator with the center-left Democratic Party, said he had visited the ship and found "a lot of suffering".

"Many people undressed in front of us to show their scabies infection," he told AFP.

"Their situation, their level of psychological stress is very, very high," added Riccardo Gatti, the chief of search and rescue at MSF.

"The ship has its limitations in terms of medical assistance: a ship is like an ambulance and people are still in the ambulance," he said.