• Concerns about migrants being 'warehoused'
• Some seafarers stuck below deck on idle ships
• Hundreds of thousands trapped in UAE, Saudi Arabia

GENEVA: Coronavirus border closures and restrictions have stranded nearly 3 million migrants around the world who want to return home but cannot, the UN migration agency said on Friday, adding some had been "warehoused" in unhygenic settings.

The International Organization for Migration report is the most comprehensive to date on the issue, covering more than 100 countries. It includes only migrants who want to return but are unable to do so because of the COVID-19 restrictions -- such as seafarers stuck on decommissioned ships, miners or construction workers.

"It should be clear that migrants can be returned home in a safe and dignified manner despite the constraints imposed by COVID-19," said Director General, António Vitorino in a statement, urging dialogue between countries.

Some stranded migrants have been confined in unclean quarters and where social distancing was impossible, placing them at risk of disease. Others face abuse, exploitation and neglect, the report said.

The worst region by far is the Middle East and North Africa which accounts for 1.275 million of the total of 2.75 million in the IOM tally. Second was Asia with nearly a million.

IOM spokesman Paul Dillon said that 648,000 stranded migrants were in the United Arab Emirates and were often construction labourers from East Africa and Asia, while 280,000 were stuck in Saudi Arabia.

Others are stuck on board idle cruise ships, often not even granted the opportunity to go above deck.

"It's a very dire situation to be trapped below deck for 6 months," he said, urging better treatment. "Migrants are key, they are central, to a robust global economy."

The IOM praised recent successes however, such as an agreement to allow 3,400 Mozambiquan miners cross back into South Africa after medical screenings, and a deal between the UAE and India on migrant workers.