Villages covered in ash after volcano erupts in Indonesia Mount Sinabung is one of three active volcanoes in Indonesia.

London -- A volcano on Indonesia’s Sumatra island sent columns of ash shooting into the sky on Monday, prompting a "code red" warning to airlines by an Australian agency monitoring volcanic ash.

Villages in the Karo region near the volcano were covered in layers of grey ash, which settled on trees and the tops of buildings, motorcycles and cars.

Villagers were forced to wear masks.

Mount Sinabung has been erupting intermittently since 2010 after being dormant for centuries.

Thousands have been displaced in the surrounding area, and continued seismic activity has kept the alert level at its highest point since June 2015.

Mount Sinabung is one of three currently active volcanoes in Indonesia, which is located on the Pacific "Ring of Fire," an area of concentrated seismic activity due to the presence of tectonic fault lines in the region.

Last year, the eruption of Mount Agung in Bali forced the cancellation of several flights, grounding thousands of tourists and sparking an evacuation order for 100,000 residents.