Mount Marapi on the island of Sumatra spewed an ash tower 3,000 metres into the sky on Sunday as scores hiked in the area
Mount Marapi on the island of Sumatra spewed an ash tower 3,000 metres into the sky on Sunday as scores hiked in the area AFP

Indonesian authorities on Thursday said they had ended a search and rescue mission for any hikers missing or killed after a volcano eruption over the weekend that left 23 people dead.

Mount Marapi on the island of Sumatra in Indonesia's west 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.

Scores were rescued but 23 people were found dead, the last on Wednesday evening, in an arduous rescue effort hampered by further eruptions and bad weather that sometimes forced workers to take shelter.

Officials said they believed every missing person had been located and evacuated dead or alive, despite initial fears some may have used unofficial hiking routes and been unaccounted for.

Hikers exploring the area must register with local authorities via an online booking system, paying a small fee and taking designated entrances.

"All victims have been found, the last victim was found dead. Therefore, based on an evaluation, the search and rescue operation led by Basarnas is closed," Agam disaster mitigation agency official Ichwan Pratama said in a statement Thursday.

"We will still activate the emergency post in case there are still families looking for their relatives, they can come here by bringing valid data."

West Sumatra police deputy chief Edi Mardianto said on Wednesday evening that all rescuers would "return to their respective units".

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.

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, and one of nearly 130 active volcanoes in the Indonesian archipelago.