A Greek far-left extremist serving 11 life terms for a string of murders is vowing to continue "until the end" with a hunger strike after judges rejected his bid for new leave from prison.

A lawyer representing Dimitris Koufodinas, chief hit man for the November 17 group that killed 23 people from 1975-2000, says her client will also refuse medical assistance.

Koufodinas, 61, is in hospital due to the hunger strike he started May 2, after authorities in his prison near the town of Volos in central Greece rejected his furlough request — a decision upheld Friday by the council of judges

The lawyer, Ioanna Kourtovik, said Friday's rejection of Koufodinas' request is "extremely unfair." He had previously been granted six furloughs.

Koufodinas was convicted in 2003.