Italian authorities have agreed to grant the Proactiva Open Arms ship access to a port to disembark 62 African migrants it has been carrying since Wednesday, the founder of the Spanish rescue mission said on Sunday.

Oscar Camps, the founder of Proactiva Open Arms, said the vessel is set to dock at the southern Italian port of Taranto on Tuesday afternoon, although the eventual destination may change.

Italy initially refused entry for the group of 73 African migrants which the Open Arms crew plucked out of a packed rubber dinghy drifting about 50 miles off Libya, suggesting that the vessel should instead put them ashore at Tripoli.

However, earlier the coastguard evacuated 11 of the group who required medical attention to the port of Augusta and Italy's Interior Minister Luciana Lamorgese signaled the country might be softening its position.

Conditions have been deteriorating as a powerful storm hit the Mediterranean, creating waves of up to three meters.

Migrants were said to be huddling under a makeshift shelter on deck as the ship rolled through choppy waters and lightning flashed overhead.

Among the group of mostly Central and West Africans are three women, two toddlers and 24 unaccompanied minors.

The Italian government has taken a hard line against immigration and has previously resisted attempts by rescue ships to land migrants in its territory.

A prolonged standoff with the Open Arms this summer was only resolved after a court ordered authorities to open a port, allowing 100 migrants to disembark.

There have been nearly 1,000 confirmed deaths on the three main migration routes across the Mediterranean so far this year, according to the International Organization for Migration.

"We need decisive action from the Italian government and form Europe to stop human traffickers," Lampedusa Mayor Salvatore Martello said from Barcelona, where he is meeting his counterpart Ada Colau to discuss the migrant crisis.

(With input from Reuters)