JAKARTA: Twenty people, nine of them from Singapore, were reported missing on Friday (May 8) after Mount Dukono on Indonesia's eastern Halmahera island erupted, spewing a smoke cloud some 10km into the air.

"Our team is on its way. It is not yet confirmed if there are injured people. Based on reports, there are about 20 people being searched for," search and rescue official Iwan Ramdani said by telephone.

Mount Dukono, located in North Maluku province, erupted on Friday at 7.41am local time (8.41am, Singapore time).

The agency maintained the alert status at the mountain at its third highest level, agency head Lana Saria said in a statement.

Iwan Ramdani, the head of the local rescue agency, told Reuters that they have deployed dozens of personnel, including police, to search for the 20 hikers trapped by the eruption.

Nine of the hikers are Singaporean and the rest are Indonesians, Iwan said.

"Our team is on its way. It is not yet confirmed if there are injured people. Based on reports, there are about 20 people being searched for," search and rescue official Iwan Ramdani said by telephone.

Authorities warned residents to refrain from any activities within 4km of the crater.

The volcanology agency also warned of the risks of volcanic mudflow when it rains.

There are not yet any reports of flight disruptions caused by the eruption.