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

NGO Mediterranea's Italian-flagged Alex was met by a strong police presence on the quayside but people were not allowed to disembark after spending two days with the rescued migrants and asylum seekers on the sailboat.

"I do not authorize any landing for those who couldn't care less about Italian laws and help the people smugglers," populist deputy prime minister Salvini tweeted as night fell.

Salvini last month issued a decree that would bring fines of up to 50,000 euros ($57,000) for the captain, owner and operator of a vessel "entering Italian territorial waters without authorization."

Mediterranea tweeted back a request to disembark those rescued, saying it had sailed to "the only possible safe port for landing," citing "intolerable hygiene conditions aboard."

"Shipwrecks and crew are exhausted... people rescued need to be cared for... this is a surreal situation and it is an unnecessary cruelty to prolong the wait." 

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.