A charity rescue vessel brought 41 shipwrecked migrants into port in Lampedusa on Saturday, the second boat to defy far-right interior minister Matteo Salvini’s bid to close Italian ports to them.

Mediterranea’s Italian-flagged Alex arrived in port where a strong police presence was waiting for them but everyone remained on board after spending two days with the rescued migrants and asylum-seekers on the sailboat.

La barca a vela Alex di #Mediterranea ha attraccato al porto di Lampedusa con 41 naufraghi a bordo. #SavingHumans pic.twitter.com/eybOlo4bZg — Mediterranea Saving Humans (@RescueMed) July 6, 2019

“In view of the intolerable hygiene conditions aboard, the Alex has declared a state of emergency and is sailing towards Lampedusa, the only possible safe port for landing,” Mediterranea said in a tweet earlier.

Salvini, who leads the Lega party and is also deputy prime minister, last month issued a decree that would bring fines of up to €50,000 (£45,000) for the captain, owner and operator of a vessel “entering Italian territorial waters without authorisation”.

Salvini tweeted after the Alex docked that the charity workers were “jackals... will they go unpunished also?”

Pur di infrangere la legge, questi sciacalli mettono a rischio la vita degli immigrati a bordo.

Rimarranno impuniti anche loro?

In un Paese serio, arresti e sequestro del mezzo sarebbero immediati: che faranno i giudici stavolta??? — Matteo Salvini (@matteosalvinimi) July 6, 2019

“Law enforcement forces are ready to intervene... in a normal country there would be immediate arrests and the boat would be impounded,” Salvini said in another tweet.

Authorities on Lampedusa last week seized another rescue ship belonging to German aid group Sea-Watch after it forced its way into port with dozens of rescued migrants on board and arrested its captain, Carola Rackete.

An Italian judge this week ordered her freed as she had been acting to save lives, a decision that sparked Salvini’s ire but may have encouraged the Alex crew.

Two other investigations, on charges of helping people smugglers and resisting the authorities, are still under way after Rackete forced her way past Italian customs vessels.

A third rescue ship, German charity Sea-Eye’s vessel Alan Kurdi, carrying 65 shipwrecked migrants rescued off Libya on Saturday, arrived and held its position in international waters off Lampedusa.

Demonstrators marched in solidarity in Berlin with the German captain of rescue vessel Sea-Watch 3, Carola Rackete. Photograph: Omer Messinger/AFP/Getty Images

In Germany, more than 30,000 people demonstrated in cities around the country in solidarity with Rackete, including 8,000 in Berlin and 4,000 in Hamburg.

“The irresponsibility of European countries obliged me to do what I did,” Rackete said in a message to demonstrators, many of whom brandished life vests.

German interior minister Horst Seehofer wrote a letter to Salvini asking him to rethink his policy, sources close to the German government said.

“We cannot be responsible for boats with people rescued from shipwrecks on board spending weeks on the Mediterranean because they can’t find a port,” Seehofer wrote.

Salvini accuses NGO rescue vessels of helping smugglers and had insisted Alex sail for the Maltese capital, Valetta, after 13 “vulnerable” people were taken to Lampedusa on Friday, leaving 41 on board.

Malta also told the Alex to go to Valletta to allow the migrants to disembark but Mediterranea said the journey would be too arduous and the boat would be likely to be seized if it did.

Photographs showed dozens of people seeking shelter from the sun under survival blankets on the narrow deck of the 18-metre sailboat.

“In these conditions it is impossible to face 15 hours of sailing,” Mediterranea’s Alessandra Sciurba said on Twitter.

Mediterranea consists mainly of left-wing activists, the avowed enemy of Salvini, who has seen his popularity and that of Lega rise thanks to his tough stance against migrant rescue ships.

A poll published in Italy’s Corriere della Sera newspaper on Saturday said 59% of Italians approved of Salvini’s closing ports to NGO vessels.

On Wednesday, only four people were rescued after a makeshift vessel carrying 86 people across the Mediterranean from Libya sank off the Tunisian coast – everyone else is missing or dead.

The Italian judge in last week’s Sea-Watch case ruled that neither Libya nor Tunisia were safe countries for migrants.