Chios, in the northern Aegean Sea, is Greece's fifth-largest island and is currently facing five separate fire outbreaks.

"The fire has not yet been contained but it is decreasing" in activity, a fire department official told AFP.

The fire service said around 400 firefighters, 85 vehicles, four water bombers and seven helicopters had been deployed, with "sporadic outbreaks" remaining mainly in the south of the island.

A Georgian woman, working as a house cleaner, was arrested on Tuesday after admitting to having thrown a cigarette butt on the ground that allegedly triggering the fire, the Greek news agency ANA and the fire service reported.

The fire forced the evacuation of hundreds of asylum seekers from a reception centre when it started on Sunday, and the evacuation of seven villages on Monday.

Authorities said the fire was also dangerously close to fields of valuable mastic trees, whose aromatic sap is used in making chewing gum, alcoholic drinks and pharmaceuticals.

Mastic is the island's most famous product, cited on UNESCO's World Heritage list.

Greece has become particularly vulnerable in recent years to fires in summer fuelled by strong winds, drought and high temperatures linked to climate change.

Weather agencies forecast a heatwave in the coming days with temperatures of more than 40 degrees Celsius (104 Fahrenheit), including in the capital Athens.