Jailed Greek far-left hitman Dimitris Koufodinas on Sunday ended a 66-day hunger strike, his lawyer said, a day after doctors warned he risked "sudden death" from disruption to multiple vital organs.

"We persuaded him to end the strike," Koufodinas' lawyer Ioanna Kourtovik told AFP.

In a statement released through Kourtovik, Koufodinas thanked "progressive people" for having shown their support in multiple protests around the country in the past months. The demonstrations were often marred by violence.

"What is happening out there is more important than what initiated it," he said.

Koufodinas, who turns 63 next week, is serving multiple life sentences for 11 murders he carried out for the extremist group November 17.

For 20 years, the group targeted industrialists, policemen, foreign diplomats and soldiers, before being dismantled in 2002.

Considered the outfit's top assassin and dubbed 'Poison Hand' by Greek media, Koufodinas began a hunger strike in January after being denied transfer to a high-security jail in Athens to be near his family.

His health has been in critical condition for the last two weeks.

On Saturday, doctors treating Koufodinas at a hospital in Lamia, central Greece, said he was in "constant possible risk of sudden death" and had suffered "multiple accumulated disruption" to vital organs.

On Sunday, the hospital said it had "gradually" begun providing Koufodinas with food and nutrients, but that his condition remained serious.

Hitman Dimitris Koufodinas began a hunger strike in January after being denied transfer to a high-security jail in Athens to be near his family
Hitman Dimitris Koufodinas began a hunger strike in January after being denied transfer to a high-security jail in Athens to be near his family AFP / Louisa GOULIAMAKI

Campaigners have accused the conservative government of Prime Minister Kyriakos Mitsotakis of vindictive behaviour against the convicted extremist.

November 17's numerous victims included Pavlos Bakoyannis, a lawmaker who was the father of Athens Mayor Costas Bakoyannis and brother-in-law to Mitsotakis.

Supporters of Koufodinas, which include anarchists, had held regular protests for weeks.

Hundreds of lawyers and intellectuals signed petitions calling on judicial authorities to respect Koufodinas' rights, and main opposition leader Alexis Tsipras had also called on the government to show leniency.

The government countered that Koufodinas -- who has held other hunger strikes in the past to secure prison leave -- was "requesting preferential treatment" and attempting to "blackmail" the judicial authorities.

The dispute has also split the Greek legal establishment. Dozens of judges have criticised a statement put out by their union that urged the authorities to "reconsider" their stance.

Greece's top administrative court, the Council of State, will in April examine Koufodinas' request to block his transfer to maximum security Domokos prison in central Greece.

Jailed since 2002, he is eligible to request release from prison in September.