"Italy is done bowing its head and obeying", Salvini tweeted on Mondy. "This time there's someone saying no".
Malta is accusing Italy of violating global norms by instructing a migrant rescue ship with 629 people aboard to stay at sea while a diplomatic standoff plays out over where it can dock. The island nation has reduced the number of migrants it has taken in over the past decade, from a high of 2,775 in 2008 to just 23 a year ago, according to U.N. statistics.
The League had promised voters during recent elections that it would take a tough stance on immigration. The migrants were bottled in Italy when northern neighbours, including France and Switzerland, closed their borders to new arrivals.
Last week, Mr Salvini said Rome should increase its deportations of migrants.
An anti-immigrant sentiment was a large part of the politician's campaign strategy - he vowed to expel hundreds of thousands of migrants already in the country.
In another Facebook post on Monday, Salvini assailed the Sea-Watch 3, another rescue ship operating in Mediterranean waters that had to wait hours to be assigned a disembarkation port over the weekend.
Tweeting on Sunday, Salvini said: "Starting today, Italy, too, begins to say NO to the trafficking of human beings, NO to the business of clandestine immigration".More news: Putin Says Russia Has Not Left the G-7 - Not True
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Mayors of Naples and Palermo in turn vented their anger at Salvini, as they stated that their cities would be more than happy to accept those in need of shelter despite the fact that both cities had been suffering from major migrant influx in the past five years. Drinking water supplies are unlimited as the ship has its own water purification system, but the passengers survive mostly on energy biscuits, prepackaged warm rice, tea and bread.
The Maltese prime minister also expressed concern over the Italian authorities' directions given to the Acquarius vessel, adding that such policies contradicted worldwide norms, and might lead to risky developments. That agreement is thought to have involved payments to certain Libyan authorities and strongmen.
"Enough!" Salvini said Monday.
"Evidently raising your voice, something Italy did not do for years, pays", Salvini said.
Malta's prime minister, who had resisted Italian pressure to take the migrants, thanked Spain's new government for defusing the crisis.
More than 100 unaccompanied minors and a number of pregnant women are on board the Aquarius. A few of the migrants were said to be injured or ill from beatings or torture, including chemical burns, they sustained from human smugglers in Libya.
Aquarius rescued 629 people Saturday night into Sunday morning - taking on people from two rubber vessels as well as "Italian navy ships, Italian coast guard ships and merchant vessels" in six different operations, MSF and SOS said on Twitter.
"The Aquarius has followed the orders of the Maritime Coordination Centre and we are awaiting the designation of a safe port to disembark", explained Nicola Stalla, the coordinator of search and rescue operations of SOS Mediterranee, according to El Pais newspaper.
Spain's new Socialist prime minister, Pedro Sanchez, ordered authorities in Valencia to open the port, saying "it's our duty to avoid a humanitarian catastrophe and offer a secure port for these people".