"This eruption is the biggest since last Sunday," said Kristianto.
Up to now, the number of people fleeing home and flocking to the evacuation shelters rose to 5,205 from that of 4,554 on Saturday, Furgon Sapid Setianto, official of national disaster management and mitigation agency posted at the disaster site told Xinhua by phone.
The authorities were relocating the evacuees at several school buildings as the students were to study on Monday, Setianto said.
Volcanologists have declared evacuation zone of 3.5 km and recommended evacuation.
Mount Lokon of 1,750 meters high is one of Indonesia's 129 active volcanoes. Its last major eruption in 1991 killed one Swiss hiker and displaced thousands of people.