ATHENS, Greece (AP) — Lawmakers in Greece were ready to support legislation to deport refugees back to Turkey as clashes between migrants persisted Thursday at overcrowded detention camps.

A three-hour fight broke out overnight between groups of migrants camping out in Greece's main port of Piraeus, leaving eight people injured and requiring treatment at nearby hospitals.

The clashes, believed to have been between Afghan and Syrian migrants, left the area strewn with rocks and broken glass. New protests were also reported at detention camps on the Greek islands of Lesbos and Chios, from where deportations to Turkey are due to start next week.

More than 50,000 refugees and migrants have been stranded in Greece after Balkan countries closed their borders to the massive flow of refugees pouring into Europe. Some 11,500 remain camped out at the border with Macedonia, ignoring instructions from the government to move to organized shelters.

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

Government officials described the violence as minor.

"In situations where there is so much tension and people have been through an ordeal, it is not surprising to have minor incidents, which are usually resolved quickly," Giorgos Kyritsis, a spokesman for a refugee crisis committee, told private Skai television.

In Athens, the government submitted draft legislation required for the landmark migration agreement reached this month by the European Union and Turkey to take full effect. The deal aims to break the smuggling rings that have brought hundreds of thousands of people from Turkey across the Aegean Sea to Greece.

Due to be voted on late Friday, the bill would upgrade Greek asylum services and set conditions for refugees and migrants to be sent back to Turkey from the Greek islands.

The returns are to start Monday, but most support staff promised by other EU countries have still not arrived on Greek islands, and the method of how to return the refugees is still being negotiated between the EU, Turkey and Greece.

An official with knowledge of the talks told the AP that deportations were likely to start from the island of Lesbos. The official asked not to be identified pending official announcements.

More than 3,000 people who have arrived in Greece since March 20 have been arrested and are being detained on Greek islands. A detention facility on the island of Chios is already nearly 50 percent over capacity, with protests by detainees occurring daily.

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Becatoros reported from Idomeni, northern Greece. Thanassis Stavrakis in Piraeus, Greece contributed.

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