ROME (Reuters) - Naples is ready to defy Italian Interior Minister Matteo Salvini and let in a charity-run ship carrying 32 migrants that is blocked in the stormy Mediterranean, the city mayor said on Thursday.

His offer adds to a growing challenge from opposition politicians to Salvini’s far-right League, which has vowed to bar migrants and make life difficult for those already here.

Both Italy and Malta are refusing to let the Sea-Watch 3, a ship operated by a German non-governmental organization (NGO), dock and set down the migrants who were rescued off Libya on Dec. 22.

Both countries say they have taken in too many migrants and accuse NGO rescue ships of acting as a taxi service for would-be refugees.

Naples’ center-left mayor Luigi de Magistris said Salvini was playing politics with peoples’ lives.

“To leave people and children in the middle of cold and stormy seas is a crime -- not simply indecent, immoral and appalling,” de Magistris told Radio Crc.

“I hope that this boat approaches the port of Naples because, unlike what the government says, we will launch a rescue operation and we will let it enter the port,” he said. “I will be the first to lead the rescue.”

Naples is hundreds of miles to the north of the Sea-Watch 3 and there was no immediate response from the boat to the offer.

Malta overnight allowed the boat into its waters to sail closer to land where the seas are less choppy, but is refusing to let it dock.

Several local politicians from opposition parties have defied Salvini’s anti-migrant policies.

On Wednesday, the mayor of the Sicilian capital Palermo, Leoluca Orlando, said he would join other cities in ignoring a new security law because it abolishes asylum protection for many migrants.

Salvini on Thursday threatened mayors with legal action.

“Anyone who helps clandestine migrants hates Italians. They will answer for their actions before the law and the history books. I will not back down,” Salvini tweeted.

“Italy’s ports are closed. We have taken in too many fake refugees. We have enriched too many people-smugglers. Left-wing mayors should think of the difficulties of their own citizens and not clandestine migrants.”

On taking office last year, Salvini barred NGO boats and moved to help Libya prevent people leaving its shores.

Some 12,977 migrants entered Italy in 2018 via boats from Libya, down 87.9 percent on 2017 and 92.85 percent on 2016, according to government data.