Thousands of asylum seekers were left homeless on Wednesday after a fire gutted Greece's largest migrant camp on Lesbos, plunging the island into crisis and sparking pledges of help from around Europe.

The 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.

Greek Prime Minister Kyriakos Mitsotakis blamed the blaze on a "violent reaction" to the virus tests, echoing an earlier report saying several fires had been lit deliberately by migrants angry at being placed into isolation after testing positive.

The EU promised to pay for 400 unaccompanied youngsters to be transported to the mainland and Germany called for EU countries to ramp up support.

EU chief Ursula von der Leyen said she was "deeply sorrowed" by the fire at the camp, which was built to house fewer than 2,800 people but routinely hosts many times that number.

"Our priority is the safety of those left without shelter," said the European Commission president.

German Foreign Minister Heiko Maas, whose country holds the presidency of the bloc, said he wanted EU counterparts to assess how they could help -- including by taking in refugees.

Norway has already offered to take 50 Syrians from Moria even though Greece has currently banned the camp's former residents from leaving the island.

An exception will be made for the 400 minors to be taken the mainland, a migration ministry source told state agency ANA.

'Where can we go?' 
 

Most of the refugees and migrants were sitting on the roadside between the camp and the port of Mytilene on Wednesday, forming long queues. 

"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.

"Two of my children are there, but I don't know where the others are," she said.

Officials immediately declared a four-month emergency and additional riot police were hurriedly flown to the island after reports emerged of security forces blocking migrants from fleeing the fire to the nearby town of Mytilene.

The UN refugee agency (UNHCR) said it was trying to find shelter for the homeless and called on everyone to show restraint, highlighting reports of tension between people in neighbouring villages and asylum seekers.

The official part of the camp -- housing roughly 4,000 people -- was completely destroyed by the fire, said deputy migration minister Georges Koumoutsakos.

Some 8,000 people live in tents and makeshift shelters outside the official camp and many of these were badly damaged in the blaze, he said.

A local town official said the perpetrators had taken advantage of strong winds and deliberately set tents on fire.

"It was premeditated. The tents were empty," Michalis Fratzeskos, deputy mayor for civil protection, told state television channel ERT.

UNHCR and rights groups have frequently criticised the Moria camp for poor sanitation and overcrowding, with hardships exacerbated after the camp was put into coronavirus quarantine.

'Titanic' effort 
 

Officials have been trying for months to build a new camp on Lesbos to replace Moria but locals have resisted, clashing with riot police earlier this year to prevent construction from going ahead.

Moria registered its first coronavirus case last Wednesday and government spokesman Stelios Petsas warned officials faced a "titanic" effort to shelter the homeless and track down those infected.

"There are 35 positive cases and they need to be isolated... to prevent an outbreak among the local population," Petsas told ERT.

Since becoming one of the main gateways into Europe for migrants and asylum seekers in 2015, Greece has built dozens of detention centres where overcrowding is common.

"It is high time that EU countries work with the Greek government to urgently relocate refugees and asylum-seekers not only to the Greek mainland but also to other EU countries," the International Rescue Committee said in a statement.

The government has in recent months moved thousands of refugees from Lesbos and other islands to the mainland.

But many refugees have been unable to find places to live or jobs after leaving the camps, with housing and cash benefits recently scaled back by the government.

Moria's first confirmed infection -- a 40-year-old man from Somalia -- was one of these cases, according to the migration ministry.