In a joint statement, the UN's maritime, labour and aviation agencies said that worldwide travel restrictions had left crews stranded around the world.

It said a key worker designation would allow crews on board vessels, such as fishing boats and cargo ships, to more easily changeover and return home.

"We are seeking the support of governments to facilitate crew changes, operations essential to maintain the global cargo supply chain," the statement said.

It added that by next month tens of thousands of seafarers will need international flights to be repatriated safely. It said that many had extended their service on board ships because they cannot be replaced.