The clashes early Friday are the latest in a series of violent incidents at shelters and gathering points across Greece, where more than 50,000 migrants and refugees are stranded following Balkan border closures supported by the European Union, AP reported.
Greece has been detaining migrants who arrived after March 20 and will begin deporting them back to Turkey next week, under an EU-Turkey agreement on migration.
The deportations will start with migrants with asylum claims considered inadmissible - a group likely to include citizens of Afghanistan.