Italy seized control Tuesday of an NGO ship it had prevented from landing nearly 50 migrants picked up off the Libyan coast, the interior ministry said.
The authorities "are in the process of taking control of the Mare Jonio, escorting the boat into the (southern) port of Lampedusa," it said.
"Questioning of the crew could following in the next few hours," it added.
Hardline Interior Minister said the action showed "that from here on in Italy has a government which defends its borders and enforces respect of its laws, above all as regards human traffickers."
Salvini had on Monday reiterated that Italy's ports were "closed" to new migrant arrivals, insisting his hardline approach to asylum seekers since last summer has effectively stopped departures from crisis-hit Libya.
He said the Italian-flagged Mare Jonio had not carried out a rescue operation but instead "aided illegal immigration".
"They can be cared for, nourished, clothed, whatever you like, but they won't get permission from me to step foot in Italy."
As the debate raged over the ship's fate, the International Organization for Migration (IOM) said another dinghy with an unknown number of migrants on board had sunk off Libya, leaving 15 survivors.
The Mare Jonio, operated by the Mediterranea collective of aid groups, took shelter from bad weather off the island of Lampedusa early Tuesday, despite being ordered to maintain a distance from the coast and turn off its engine, according to its mission head and captain.
"We have people on board who are sick, I have to take them to a place of safety and there are two-metre (six-foot) high waves. I'm not turning off the engine," Captain Pietro Marrone told the authorities, according to the Avvenire daily.
'No other choice'
"The weather conditions were impossible. We had no other choice," mission head Luca Casarini said.
"We are sailing under an Italian flag, they cannot forbid us to disembark," he added, according to AGI news agency.
A 25-year old with suspected pneumonia was evacuated to Lampedusa for medical attention.
Salvini, who heads up the far-right League, has repeatedly declared Italian ports closed to NGO rescue vessels, previously leaving several of them stranded at sea in a bid to force other European countries to take their share of asylum seekers.
He issued a directive on Monday saying ships rescuing people in areas of the Mediterranean under Libyan responsibility, during operations not coordinated by the command centre in Rome, have no right to use Italy as a port of safety.
Any infringement of international maritime or Italian law "can be read as a premeditated action to bring illegal immigrants to Italy and facilitate human trafficking", he said.
On Tuesday, he said the ministry was creating a commission of "experts and police" to ensure his directive - which lays down rules about rescues at sea - was enacted.
The Italian Refugee Council said it was "extremely concerned" over the directive, which "assumes that Libyan ports can be considered safe and that docking at Tunisian and Maltese ports is possible".
"It takes no account of the dramatic reality," council director Mario Morcone said in a statement.
"We act as if the countries with which we share the Mediterranean were the Netherlands, Germany or Sweden. But this is clearly not the case," he said.
Deputy Prime Minister Luigi Di Maio confirmed that the authorities were boarding the vessel which had refused an order to switch off its engine.
He accused the ship's crew of "disobeying an order from the Libyan coast guard by taking on board the migrants".
Since Italy's populist government came to power last year and began a crackdown on rescue vessels, "we have seen an exponential increase in the number of deaths compared to the number of migrants landing," the refugee council said.
Some 152 people have died in 2019 so far, while 471 have reached land in the central Mediterranean.
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