Three hikers -- two Singaporeans and a local -- died in an eruption Friday of Indonesia's Mount Dukono volcano where they found themselves in a no-go zone, officials said.
The eruption on Halmahera island sent an ash cloud about 10 kilometers (6.2 miles) into the air, with no towns of villages near enough to face any immediate threat.
Twenty hikers were on the slopes when disaster struck, North Halmahera police chief Erlichson Pasaribu told reporters at a volcano monitoring station in Mamuya village.
Nine were from Singapore and the rest Indonesian, AFP reported.
"To date, 15 climbers have safely descended," Erlichson said several hours after the early-morning eruption.
The bodies of the deceased were still on the mountain, he added, without elaborating on the whereabouts of the last two hikers.
"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," Erlichson 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 Center for Volcanology and Geological Hazard Mitigation (PVMBG) has warned tourists and climbers not to come within four kilometers (2.5 miles) of the volcano's Malupang Warirang Crater after scientists spotted an uptick in seismic activity.
Erlichson 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," he said.
Lana Saria, head of the government Geology Agency, said Friday's eruption was accompanied by a "booming sound" and a thick column of ash and smoke rising 10 kilometers 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, Lana added, and risked disrupting transportation services.
There are no settlements within a radius of about 9km from 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 currently on level two of Indonesia's four-tiered alert system.
Erlichson urged hikers to stay away to avoid a repeat of Friday's avoidable disaster that has forced rescuers to deploy into in "tough terrain" even as the volcano continues rumbling.
"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," he said.
