Police and detainees clashed Wednesday at a former military base in southern Greece where foreign nationals suspected of violating immigration laws are held pending deportation.
Financially struggling Greece is the main gateway for Asians and Africans trying to illegally cross into the European Union. Most end up stuck in the country, up to 10 percent of whose population is now of foreign origin.
A police statement says officers fired tear gas at detainees alleged to have thrown roof-tiles at them. It also said detainees set fire to buildings in the complex outside the town of Corinth.
Police arrested 47 Afghans suspected of taking part in the clashes.
Immigrant rights groups, including the Movement United Against Racism and the Fascist Threat, claimed the trouble on the fringes of Corinth started after police beat up a detainee who had refused food to protest the extension of his detention. In a joint statement, the groups, among them one representing the Pakistani community, also said the fires were started by tear gas canisters fired by police.
More than 5,000 people are held in similar complexes across Greece, and rights groups say hundreds are refusing to eat in reaction to the prolongation of their detention, which under Greek law can reach a maximum 18 months. Human rights groups have repeatedly criticized the detention conditions.
The unchecked wave of illegal immigration in recent years, which coincided with a spike in crime, contributed to the meteoric rise of a once-marginal extreme right-wing party with neo-Nazi leanings that entered Parliament last year.
The Golden Dawn party, whose supporters have repeatedly been linked with violent attacks on immigrants, is currently Greece's third most popular, polling at around 10 percent.