More than 6,000 residents living near the Mount Sinabung volcano on Indonesia's Sumatra island were told to evacuate Wednesday following a sharp increase in volcanic activity.

Mount Sinabung has erupted intermittently since late 2013. Sixteen people were killed and tens of thousands were temporarily displaced during an intense period of eruptions early last year. The alert for Sinabung has been raised to the highest level, said Sutopo Purwo Nugroho, a spokesman for the National Disaster Management Agency.

The lava dome at Sinabung has grown in volume to more than 3 million cubic metres, making it unstable, Mr Sutopo said.

"There is a risk for the collapse of the dome followed by block-and-ash flows as far as 7 kilometres to the south-east," he said.

Mr Sutopo said 2,053 families, or 6,179 people, living in eight hamlets on the southeastern slope of the volcano were affected by the evacuation order.

"Priority will be given to 370 families within the radius of three kilometres," he said. Nearly 2,000 people are still living in temporary shelters as a result of last year's eruptions.

Others either returned to their homes or were relocated elsewhere.