Indonesia: Seven farmers die after Sumatra's Mount Sinabung volcano erupts

People living in temporary shelters had begun moving back to their farms for economic reasons,

The death toll from a volcanic eruption in western Indonesia rose to seven, officials have said.

There are fears that more people could have been trapped by the hot ash after Mount Sinabung unleashed a series of fresh eruptions on Saturday afternoon.

Mount Sinabung is a highly-active volcano on Sumatra Island. Disaster agency spokesman Sutopo Purwo Nugroho said three people are in critical condition.

Officials had earlier said six people died after the volcanic eruption. "Nine people were struck by the hot clouds. Six died, and three others remain critical with burns" he said, adding that the injured people have already been taken to the hospital.

The victims were farming within the "red zone" when they were consumed by pyroclastic clouds. The "red zone" is referred to an area which is four kilometres from Sinabung, declared off limits by government authorities for safety reasons.

Sutopo said that these fast-moving waves of hot gas and rock can reach up to 700 degrees celsius as they roar down the sides of the volcano.

In late 2014, the residents of Gamber village were asked to evacuate due to the unacceptable risk from lava flows, dense ash and falling volcanic rock.

Sutopo said: "It is not known exactly how many people were in Gamber village when the hot clouds descended." He added that the Search and rescue teams were carefully polishing the homes and farms in Gamber village and they were suspicious of the risk of further eruptions.

"There shouldn't have been any public activity (within the red zone)," he said.

Many people who were living in temporary shelters had begun moving back to their farms for economic reasons, despite repeated warnings, he added.

Tens of thousands of people have been displaced since Sinabung had erupted back to life in 2013 after a period of inactivity. It erupts periodically by sending columns of ash several kilometres into the sky, and sometimes claiming lives of people.

Sixteen people had died during a particularly fierce eruption in 2014, and Sinabung remains at the highest alert level.

Sinabung is regarded as one of 129 active volcanoes in Indonesia, which is located on the Pacific Ring of Fire, a belt of seismic activity running around the basin of the Pacific Ocean.