Villagers living near Ecuador's Tungurahua volcano have been advised to leave their homes after the volcano erupted.

Thick clouds of poisonous gas, ash and steam have poured in the skies above the town of Banos, 140km from the Ecuador capital of Quito.

One explosion sent a plume of ash 4km into the sky and rivers of lava are pouring down the volcano's flank, according to the Geophysical Institute of Ecuador (IGEPN).

Airborne volcanologists reported that the superheated magma in the volcano's crater was high enough to be visible to the naked eye. Much of the ash has spread in southwest and western directions.

The institute said: "It is recommended to the authorities and the general public to maintain protective measures and preparedness. We do not rule out the possibility of [it] generating more pyroclastic flows and ash falls."

Tungurahua, meaning "Throat of Fire" in the Quechua language, is one of eight active volcanoes in the Andean nation. It has erupted annually almost every year in the last decade and last erupted in November.

Check out the latest photographs of the eruption of Tungurahua volcano in Ecuador

Ecuador's Tungurahua volcano spews lava ash and pyroclastic material into air in Tungurahua, 21 August.REUTERS/Gary Granja
Ecuador's Tungurahua volcano spews lava ash and pyroclastic material into air in Tungurahua, 20 August.REUTERS/Gary Granja
Ecuador's Tungurahua volcano spews lava ash and pyroclastic material into air in Tungurahua, 19 August.REUTERS/Gary Granja
Ecuador's Tungurahua volcano spews lava ash and pyroclastic material into air in Tungurahua, 21 August.REUTERS/Gary Granja
Ecuador's Tungurahua volcano spews lava ash and pyroclastic material into air in Tungurahua, 21 August.REUTERS/Gary Granja
Ecuador's Tungurahua volcano spews large clouds of gas and ash near Banos, about 178 km south of Quito.REUTERS/Gary Granja
American tourists are seen at a tree house, which is used to observe Tungurahua volcano activity from 1.2 km (0.75 miles) of the volcano's crater in Ecuador.REUTERS/Gary Granja