Nobody was injured in Monday's riot at the Moria camp on the eastern Aegean island of Lesbos, but three prefabricated cabins used as offices by asylum officials were severely damaged.
Police said about 70 migrants, mainly Pakistani and Bangladeshi nationals, threw stones at the cabins and then set them on fire with burning blankets.
Riot police detained 22 suspected rioters.
More than 60,000 refugees and other migrants hoping to move deeper into Europe are trapped in
Greece following a series of Balkan border closures.
Some 15,000 of these are on the eastern islands.
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