The 180 migrants aboard the Ocean Viking rescue ship wait to disembark at Sicily's Porto Empedocle, Italy on July 6. Photo: VCG

Thousands of asylum-seekers were without shelter on Thursday after a fire gutted Greece's largest migrant camp, prompting wrangling among European nations over their responsibility toward refugees and calls for urgent reform of the current system.

A second fire on Wednesday evening aggravated the crisis on the island of Lesbos, where authorities have declared a state of emergency.

The first blaze, which began hours after 35 people tested positive for coronavirus at the Moria camp, sent thousands fleeing for safety into surrounding olive groves - but nobody was seriously hurt.

While European countries from Germany to Norway - along with EU chiefs - responded with offers of help, Greek officials sought to blame migrants for the fire.

Stopping short of alleging arson, Greek Prime Minister Kyriakos Mitsotakis said the blaze was down to a "violent reaction" in the camp to virus testing.

Migration minister Notis Mitarachi said asylum-seekers had started the fire because of quarantine measures imposed after the positive tests.

Most of the migrants were sitting on the roadside between the camp and the port of Mytilene on Wednesday evening.

"What are we going to do now? Where can we go?" said Mahmout, an Afghan, as his compatriot Aisha searched for two of her children.

"We lost everything" in the fire, said Cornille Ndama from DR Congo.

"I have nothing, nothing with me, and yet we don't know where we are going to sleep," he said.

Of 3,500 migrants whose dwellings were destroyed, the most vulnerable would spend Wednesday night on a ferry at a nearby port, with two Greek navy vessels providing additional sleeping berths on Thursday, said Mitarachi.

On Thursday, EU vice-president Margaritis Schinas was set to visit the camp before meeting Mitsotakis in Athens.

AFP