More than 800 migrants who were plucked to safety in the Mediterranean disembarked from a charity rescue vessel in Sicily on Sunday, with most set to be transferred to two waiting quarantine ships.

Red Cross workers helped the migrants -- some wrapped in blankets, many barefoot -- off the Sea Eye 4, which had begged Italy to allow it to dock after carrying out multiple rescue operations.

Save the Children staff said they had been told there were around 170 minors aboard, but it was not yet clear how many were travelling with families and how many were unaccompanied.

Some of the migrants raised their arms in celebration and cheered as the red ship pulled into the port of Trapani in western Sicily. Others sat with their legs dangling over the side, looking tired and drawn.

The Sea Eye 4 was already carrying nearly 400 people who had been pulled to safety at sea when it raced to the rescue of another 400 people crowded onto a wooden boat on Thursday.

It was given permission to dock just hours after a fellow charity delivered urgently needed relief supplies, including food and blankets, and after repeated appeals for help, the German NGO Sea Eye told AFP.

After coronavirus tests, the adults without health problems were to be placed on quarantine ships.

The UN's human rights agency said on Twitter it was "relieved that once again Italy has welcomed people whose lives were in danger at sea, and who were saved by the fundamental work of NGOs".

Italy is one of the main points of entry into Europe for migrants sailing mainly from Libya and Tunisia, with tens of thousands of people seeking to cross the central Mediterranean each year.

Nearly 55,000 migrants have disembarked in Italy this year, compared with just under 30,000 last year, according to interior ministry figures.

Unlike between 2014 and 2017, when more than 90 percent of migrants landing in Italy had set off from Libya, the arrivals are now "well distributed" between Libya and Tunisia, according to Matteo Villa from the Institute for International Political Studies (ISPI).

More than 70 percent of those setting off from Tunisia are Tunisian, while most people attempting the perilous crossing from Libya are Bangladeshis who had been in the crisis-torn country for some time, he said.

The Ocean Viking, a charity vessel run by SOS Mediterranee, was meanwhile Sunday still looking for a port after rescuing more than 300 people.

"As weather conditions deteriorate, the medical team expects an increase in health problems among the 306 castaways still on board," SOS Mediterranee said on Twitter.