Migrants being detained aboard one of two tourist cruise vessels at sea have started a hunger strike, an NGO claimed on Tuesday. 

Writing on Twitter, rescue hotline Alarm Phone said that the desperate migrants had recently made contact with them, detailing attempts of suicide and hunger strikes.

"The prisoners say 'anxiety, hopelessness and depression increased' and that there is no sufficient healthcare and food," the NGO said.  

Malta closed its ports to asylum seekers in April and told the EU it could not guarantee the resources needed to conduct rescues at sea, because of the COVID-19 pandemic.

A Captain Morgan vessel, the Europa II, has been at sea just outside Malta's territorial waters for almost two weeks with 57 migrants on board. A second boat also owned by the cruise company, the Bahari, has also been sent to house migrants 13 nautical miles off Malta. 

Prime Minister Robert Abela has defended the move, saying that Malta was abiding by international obligations to coordinate rescues.

He told Parliament last week that the vessels were each costing around €3,000 daily. 

Alarm Phone did not say which of the two vessels the people who had contacted them were being held on.  

A spokesperson at the Office of the Prime Minister had not commented by the time of writing.