Indonesian rescuers were searching on Wednesday (Dec 6) for the final hiker who went missing after a volcano eruption that left 22 other people dead, but hopes were fading three days after the disaster.

Mount Marapi on the island of Sumatra spewed an ash tower 3,000m - taller than the volcano itself - into the sky on Sunday as 75 people hiked in the area.

Hundreds of rescuers have worked for days to find the missing hikers, who have been carried down the mountain in bodybags in an arduous search effort hampered by further eruptions and bad weather that forced workers to intermittently take shelter.

"There were many rumours and unclear reports. Let us make it clear, we still don't know the whereabouts of this one victim," Abdul Malik, head of the Padang Search and Rescue Agency, told reporters.

It came after Suharyono, West Sumatra police chief who goes by one name, told reporters late on Tuesday that the last hiker was feared dead, which has not been confirmed by the rescue officials on the ground.

"23 people are suspected to have died. We all prayed they all could be rescued but there was nothing we could do, God and nature had made a decision," he said.

On Wednesday morning the volcano, which means Mountain of Fire, was still billowing a column of smoke into the sky, an AFP journalist said.