Police and detainees have clashed 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.

A police statement says officers fired tear gas on Wednesday at detainees alleged to have thrown roof-tiles at them and set fire to buildings in the complex outside the town of Corinth.

Police arrested 47 Afghans suspected of taking part in the clashes.

An immigrant rights group claimed the trouble started after police beat up a detainee who had refused food to protest the extension of his detention.

More than 5,000 people are held in similar complexes. Human rights groups have repeatedly criticized the detention conditions.