UN Secretary-General Antonio Guterres called Friday for countries to relieve ship crews stranded at sea for long periods due to lockdowns imposed to contain the coronavirus pandemic. 

"The Secretary-General calls on all countries to formally designate seafarers and other marine personnel as 'key workers' and ensure crew changeovers can safely take place," a statement issued by the United Nations said. 

Guterres is "concerned about the growing humanitarian and safety crisis facing seafarers around the world." 

Travel restrictions and lockdowns have meant that hundreds of thousands of seafarers have been stranded at sea for months, the statement said

"Unable to get off ships, the maximum sea time stipulated in international conventions is being ignored, with some seafarers marooned at sea for 15 months," it said.

Maritime transport makes up 80 of global commercial trade and is crucial to the movement of medicines, food and critical goods used in the fight against the pandemic, Guterres said.