On Monday, Indonesia ordered 100,000 residents living near a volcano spewing columns of ash to evacuate immediately.
"The potential for a larger eruption is imminent," the Disaster Mitigation Agency (BNPB) said.
Sutopo, a spokesman for the agency, said there had been no casualties so far and 40,000 people had left the area, but tens of thousands still needed to move.
Mount Agung last erupted in 1963, killing more than 1,000 people.
—Reuters and CNBC's Uptin Saiidi contributed to this report.