Greek authorities say a fight broke out overnight between groups of migrants camping out in Greece's main port of Piraeus, injuring eight.

The coast guard said Thursday the three-hour fight, believed to have been between Afghans and Syrians, broke out at about 10 p.m. Wednesday. The aftermath was visible Thursday, with rocks and broken glass strewn on the street.

Eight people were being treated in a nearby hospital.

More than 50,000 refugees and migrants are stranded in Greece after Balkan countries closed their borders to the massive refugee flow. Under a European Union-Turkey agreement, those arriving from the nearby Turkish coast to Greek islands since March 20 will be sent back.

Hundreds of those camping out in Piraeus were boarding buses Thursday for refugee camps elsewhere in Greece.