Three hikers killed in Indonesian volcano eruption

Three hikers have died in an eruption of Indonesia's Mount Dukono volcano, officials said.

The eruption on Halmahera island sent an ash cloud about 10km into the air, with no towns or villages near enough to face any immediate threat.

Twenty hikers were on the slopes when disaster struck, a local police chief told reporters at a volcano monitoring station in Mamuya village.

He said nine were from Singapore and the rest Indonesian.

"To date, 15 climbers have safely descended," he said several hours after the early-morning eruption. He did not comment on the whereabouts of the last two among the 20.

A tour guide who was on the slopes when the eruption happened, said he arrived with a tour group yesterday and found the volcano acting "a bit strange".

"This was the first time I'd seen it so quiet. I told the guests that a major eruption is going to happen because the volcano is accumulating pressure at the bottom of the crater. And my prediction turned out to be correct," he said.

When the eruption happened there were two groups of tourists, about 15 in total, at the crater rim, he said.

He was with two German hikers who "survived because we were in the safe radius," said the guide, describing this as the biggest eruption of Mount Dukono he had ever witnessed.

"Previously, when there was an eruption, there would be a single blast and then it was over. This time, the eruption started at 7.42 and by the time we came down the intensity was still the same, rocks were still coming out of the crater."

The bodies of the three deceased were still on the mountain.

"Due to ongoing eruptions, the situation is still considered unsafe for evacuation. So, the joint team is still waiting for the right time to begin the search," the police chief said.

Some of the hikers had suffered minor injuries and were taken to hospital for treatment.

The group's guide and a porter were taken to the police station and could face criminal charges for taking hikers into a prohibited area, added the police chief.

Since December, the Centre for Volcanology and Geological Hazard Mitigation (PVMBG) has warned tourists and climbers not to come within 4km of the volcano's Malupang Warirang Crater after scientists spotted an uptick in seismic activity.

Police said the hikers had ignored social media appeals and warning signs put up at the entrance of the trail to stay away.

"Local residents understand and don't want to climb. Many (hikers) are foreign tourists who wish to create (social media) content."

The head of the government Geology Agency said the eruption was accompanied by a "booming sound" and a thick column of ash and smoke rising 10km from the summit of Mount Dukono.

"The direction of the ash distribution leans northward, so residential areas and Tobelo City need to be vigilant for... volcanic ash rain," she said in a statement.

The smoke could be dangerous for public health, she added, and risked disrupting transportation services.

There are no settlements within a radius of about 9km of the volcano.

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

The Southeast Asian country has nearly 130 active volcanoes.

Mount Dukono is on level two of Indonesia's four-tiered alert system.

"After this incident, we will be strictly monitoring posts that hikers can pass. So no hiking as long as the status remains at level 2," the police chief said.