Indonesia's Mount Ruang erupted early Tuesday, forcing residents to evacuate the island, while there were no immediate reports of casualties, according to local authorities.

The eruption occurred shortly after authorities lowered the alert level of the volcano in central Indonesia from the highest. However, it was promptly raised back to the peak following the eruption.

The Center for Volcanology and Geological Hazard Mitigation expanded the no-activity radius for residents to 7 kilometers as hot stones spewed by the 725-meter volcano in North Sulawesi Province fell outside the earlier-set 6 km radius, reaching the main refugee camp.

National Disaster Mitigation Agency spokesman Abdul Muhari told a press conference that the authorities have decided to relocate all 834 Ruang Island residents.

About 12,000 residents of nearby Tagulandang Island will also be evacuated to another island to its north.

"We have recommended that residents not remain in coastal areas as a lot of volcanic material has been falling to the bottom of the sea," the spokesman said.

"Based on our past experience in 1871, falling volcanic material can cause a tsunami. A tsunami caused by a collapsed volcano can't be predicted...unlike that of an earthquake," he added.