The agencies said they recognised that the pandemic had led to states bringing in new border controls, but said these measures "should not result in the closure of avenues to asylum, or in forcing people to either return to situations of danger or seek to land clandestinely, without health screening or quarantine".

The people at sea are mostly fleeing unrest and persecution in Myanmar - which is facing trial accused of genocide against the Rohingya minority. Hundreds of thousands of people have fled violence in Myanmar in several waves in recent years - the worst crisis came in 2015 when thousands took to boats and became stranded at sea after Thailand closed people smuggling routes through its territories.

The statement from the UNHCR, IOM and UNODC said they were concerned about "reports that boats full of vulnerable women, men and children are again adrift in the same waters, unable to come ashore, and without access to urgently needed food, water and medical assistance".