Thousands of migrants were forced to flee to safety on Monday when their camp on the Greek island of Lesbos was badly damaged in a fire apparently set on purpose, police said.

No casualties were reported but tents at the Moria camp were "almost entirely destroyed" and containers that provide additional accommodation and health and registration services were damaged, said a police source in Athens.

Firefighters were prevented from tackling the fire early on by clashes that broke out among rival nationalities in the camp, reports said.

"Between 3,000 and 4,000 migrants fled the camp" to the surrounding fields, with strong winds fanning the flames also hampering firefighters, the police source said.

The officer said there was "no doubt" that the fire had been set on purpose by those inside.

Some 150 minors housed at the camp were evacuated to a children's village on the island, the officer said.

Earlier on Monday, tensions rose in Moria owing to a rumor that migrants were about to be deported en masse to Turkey, state agency ANA reported.

Overcrowding

Another two fires broke out in the olive groves near Moria but were brought under control before the third blaze erupted at the camp.

There are now more than 60,000 refugees and migrants in Greece, most of them seeking to travel to Germany and other affluent EU countries.

But they are unable to do so after several eastern European and Balkan states shut their borders earlier this year.

Human rights groups have repeatedly criticized the condition of those migrant camps in Greece, pointing to overcrowding and unsanitary living conditions.

The situation is particularly acute on Lesbos and other eastern Aegean islands facing Turkey, where most of the migrants land and are held for registration.

Island residents have also staged protests to demand the transportation of the migrants to the mainland.