Migrants at the Moria camp threw stones and sprayed water during a visit by the Greek migration minister and a Dutch minister, officials said.
Police firing tear gas and reports that several refugees and migrants had been injured. Black smoked billowed into the sky after refugees set fire to rubbish bins within the fenced camp near the village of Moria, a few miles from the island’s main port, Mytilini.
The trouble started in a wing of the camp where minors are held and then spread. Riot police were conducting operations, police said.
There were reports on social media that refugees had taken control of the camp, chanting “Freedom, freedom” over the public address system.
The clashes broke out after a Greek policeman reportedly slapped or hit a minor, refugees inside the camp said.
More than 4,000 refugees and migrants, including women and children, are kept in the camp, which is ringed by razor wire and guarded by Greek police and soldiers. They are among more than 50,000 migrants and refugees who are stranded in Greece after its northern neighbour, Macedonia, closed its border in March, after similar action was taken by other Balkan countries.
Frustration has been growing for weeks, with violence breaking out on Aegean islands such as Lesbos and Chios and at Idomeni on the Greek border with Macedonia, where Macedonian police have fired rubber bullets and stun grenades at refugees trying to scale the frontier fence.
The refugee camp on Lesbos was turned into a closed detention centre after a controversial EU deal to send economic migrants back to Turkey was announced. Under the EU-Turkey agreement, migrants who have arrived illegally in Greece since 20 March are to be sent back to Turkey if they do not apply for asylum or if their claim is rejected.
For each Syrian migrant returned to Turkey, the EU is to take in another Syrian who has made a legitimate request. Earlier, 49 migrants from Afghanistan, Iran, Pakistan and Myanmar became the third group of migrants to be returned to Turkey under the deal.