A police hunt for migrant escapees was under way in Athens on Sunday after a detention camp riot left 10 officers injured, authorities said.
"There were some escapes and we are currently trying to locate them," a police spokesman said.
The riot broke out late Saturday at Greece's main migrant holding centre in Amygdaleza, northeast of Athens, where some 1,200 mainly Afghan and Pakistani migrants are kept under police guard.
The detainees set fire to mattresses and their living quarters, and threw stones and other objects at riot police dispatched to subdue them.
According to the police, the unrest began when the detainees were told that their maximum stay in the camp would be extended to 18 months from 12 months.
The police were unable to confirm how many migrants were hurt in the incident.
Amygdaleza is one of several detention centres set up since last year to assist in the repatriation of thousands of undocumented migrants.
Rights groups charge that the migrants have been subjected to abuse by police in the camps, and are denied proper health care.
Last week, leftist rights group KEERFA said Muslim detainees had been beaten by guards during prayers.
In July, the same group reported the death of an Afghan detainee from a lung infection that his guards had allegedly ignored for months.
Greece is a major entry point into the European Union for migrants and refugees fleeing war-torn and impoverished countries in Africa, the Middle East and the Indian subcontinent.