Indonesian rescuers were searching on Wednesday 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 3,000 metres (9,800 feet) -- 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.

- 'Some jumped' -


Fifty-two people were rescued since the eruption and some of the survivors have described their panic after it started.

"I was zig-zagging, going down around 30 to 40 metres" to a trekking post, Ridho, 22, told AFP from a bed in a nearby hospital.

"The eruption sounded loud, I took a look behind and then immediately ran away as everyone did. Some jumped and fell. I took cover behind the rocks, there were no trees there."

Suharyono said Tuesday evening that two of the 75 hikers were police officers, one who survived and the other one he suspected had died.

"They both just wanted to see the volcano, they were off duty," he said.

"One of them survived and had a broken arm, he is being treated by doctors. For the other one, we suspected he died. Let's wait for confirmation."

The head of Indonesia's volcanology agency, Hendra Gunawan, said Marapi has been at the second level of a four-tier alert system since 2011, and a three-kilometre exclusion zone had been imposed around its crater.

He appeared to blame hikers after the eruption for going too close to the crater, saying the agency recommended no activity in that area.

The official number of hikers given by officials was sourced to an online registration system but officials warned there could have been more on illegal routes.

"Maybe there were hikers who were not registered, and sometimes illegal hikers did not want to pay, they just climbed," said Suharyono.

Indonesia experiences frequent seismic and volcanic activity due to its position on the Pacific "Ring of Fire", where tectonic plates collide.

Marapi is the most active volcano on Sumatra island and one of the archipelago's nearly 130 active volcanoes.