Two people have been killed and 21 injured in a riot at Korydallos prison in Athens.
The violence is said to have been caused by a conflict between rival Albanian and Pakistani gangs. Inmates attacked each other with makeshift knives.
International human rights groups have previously expressed concern over inhumane treatment of detainees and overcrowding at Korydallos.
In February 2014, some Korydallos prisoners took part in a hunger strike to protest what they said were the prison’s appalling living conditions.
Detainees reported being forced to beg for medical care and media reports discovered the prison’s hospital was 140 people over capacity.
Many of the prisoners suffered from such contagious diseases as HIV, tuberculosis and hepatitis.