Hikers evacuated as Indonesia volcano spews ash tower

JAKARTA - A volcano in western Indonesia erupted on Sunday, belching a column of ash around three kilometres into the sky and forcing the evacuation of dozens of hikers.

Mount Marapi on the island of Sumatra, with a peak of 2,891 metres, is on the third-highest alert level of Indonesia's four-step system and authorities imposed an exclusion zone around its crater.

There were no immediate reports of damage or casualties after the eruption, but officials said several dozen hikers were "unaccounted for".

One of those still coming down the mountain was 19-year-old student Zhafirah Zahrim Febrina, whose mother Rani Radelani shared a video from her daughter who is seen covered in ash and appealing for help.

"She WhatsApped. She said she didn't have any strength. She was hiking since Friday," her mother told AFP.

"She is coming down along with her friends."

Rescue teams have been deployed to help bring mountaineers down to safety, the West Sumatra natural resources conservation agency said.

"The... agency team are conducting evacuations. Hopefully there are no fatalities and everyone is safe," Dian Indriati, the interim head of the agency said in a video statement.

It said 70 hikers had checked in since Saturday via an online booking system, with 42 accounted for as of 5pm local time.

However, the local disaster agency later said 47 hikers had been on the mountain, with 28 still to be evacuated.

Casualty figures in Indonesia can often fluctuate due to miscounting.

Some hikers also may not notify authorities about their presence when entering or leaving such areas, so the true number of unaccounted hikers remains unclear.