VALLETTA - The Maltese authorities on Sunday finally allowed 58 migrants from the Aquarius ashore after days waiting in rough seas on board the rescue ship that can no longer go to port after its flag was pulled.

The group, which includes 35 women and children, was transferred to a Maltese patrol boat in international waters and then brought to shore.

The UN's refugee agency said the migrants - among them Libyans, Afghans and people from sub-Saharan Africa - would be sent on to four European countries following a deal struck earlier this week, ending the latest tense standoff over people rescued at sea. Among the group are 18 children, 17 women - one of whom is five-months pregnant, 23 men and a dog called Bella, the first animal rescued with migrants in the Mediterranean. "We hope that they will leave Malta in a few days," UNHCR representative Paolo Biondi told AFP.

France will take in 18 of them, Germany and Spain will each accept 15 and Portugal will re-home 10.

The rescue ship has been operating under a Panamanian flag but last weekend, Panama said it would revoke its registration following a request from Italy's populist government.

Deflagging a vessel leaves it unregistered and unable to set sail.

Last month, the Aquarius spent 19 days docked in the French port of Marseille after Gibraltar revoked its flag, only setting sail again last week after first acquiring Panamanian recognition.

Several other rescue vessels impounded in Valletta are locked in protracted legal battles.

The latest group of migrants were rescued last Monday from two boats plying the perilous route between North Africa and Europe.

In a statement, UNHCR hailed the deal which allowed the migrants ashore, saying it happened in a climate of "growing uncertainty over future search and rescue capacities" in the Mediterranean.

And it urged European nations to "rapidly accelerate" their efforts to improve the arrangements for those rescued at sea to come ashore. "Doing so will save lives."

Aid groups say the absence of civilian boats in the Central Mediterranean means that while numbers of people leaving North Africa have dropped, the risk of dying is more than three or four times higher than a few months ago.

The UN agency also expressed concern about the implications of deflagging the Aquarius.

"The de-registration of the Aquarius is deeply worrying and would represent a dramatic reduction of search and rescue capacity at precisely the moment when it needs to be stepped up," it said.

With no flag, Aquarius was expected to head to its home port of Marseille where it faces an uncertain fate, despite an international appeal for a new flag so it can resume its work.

"Reinforcing search and rescue capacity on the Central Mediterranean and disembarkation in places of safety, has to be everyone's goal," said UN High Commissioner for Refugees Filippo Grandi.

"We are talking about people's lives. Refugees and migrants cannot be continually put at risk while States argue over their responsibilities."

Both Italy and Malta have taken a hard line on migrants, saying they have to shoulder an unfair share of the burden.

Chartered by Doctors Without Borders (MSF) and SOS Mediterranee, the Aquarius was the only civilian ship working to rescue migrants in the Central Mediterranean, although aid groups say they hope to have more operational soon.