The Aquarius, a rescue vessel operated by aid organizations Doctors Without Borders (also known as Médecins Sans Frontières) and SOS Mediterranée, was forced to wait in the Mediterranean Sea between Italy and Malta after failing to receive guidance from Italian authorities.
Italy says its decision to shut its ports to hundred of migrants aboard a charity ship is firm, as a clash between Rome and Paris over migrant policy heats up.
Since Italy's navy had coordinated the initial rescue effort, and even transferred some of the migrants its own navy had saved to the rescue ship staffed by volunteer aid workers, it was obliged by worldwide law to ensure their safety.
Earlier, Aquarius crew member Alessandro Porro told news channel Sky TG24, that the ship was north of Malta and had "received no communications from the Maltese authorities". Spain's prime minister offered to let it port in Valencia.
"Turning this into a political weapon is despicable.it is clear that Europe must act more wisely, but we can not let these people die at sea".
In this photo taken on May 6, 2018 the French NGO's ship Aquarius, a search and rescue ship run in partnership between "SOS Mediterranee" and Doctors without borders (MSF), is seen some 24 nautical miles off the Libyan coast.
In a statement late Sunday after speaking with his Italian counterpart, Mr Muscat refused to let the ship dock in a Maltese port, but said Malta would conduct emergency medical evacuations if necessary.
Italy's new interior minister, Matteo Salvini, said on Sunday that from now on, "Italy, too, begins to say NO to the trafficking of human beings".
On Monday afternoon, Spain offered to allow the migrant-rescue ship to dock at the port of Valencia "to help avert a humanitarian catastrophe, " though it remained unclear whether or not the ship was able to make the journey to Valencia.
European Union law requires that asylum seekers register in the first safe country they reach, but frontline countries such as Italy and Malta have said the burden needs to be shared out across the bloc.
"The rescues will continue and it is crucial that European countries talk amongst themselves to find acceptable solutions" to bring to shore migrants stranded in the Mediterranean, she said. "The same can not be said of France, which has often adopted much more rigid and cynical immigration policies", the Italian government says.
The Aquarius took on the migrants from human traffickers' boats in the Mediterranean Sea on Saturday.
Under the global law, people rescued in the sea should be brought to the closest and safest port for assistance. As such Malta will not take the said vessel in its ports, the statement said. The voyage to the Spanish port of Valencia is expected to take four days.
The Aquarius and its passengers were caught up in a crackdown promoted by the right-wing partner in Italy's new populist government, which has vowed to stop the country from becoming the "refugee camp of Europe".
That has put pressure on Italy and Greece, the entry points for hundreds of thousands of people fleeing war and poverty in the Middle East, Africa and Asia since 2015.