Nearly 76,000 people have evacuated areas around Bali's Mount Agung, which is threatening to erupt soon, with President Joko Widodo yesterday visiting the evacuees in relief shelters.
The number of people fleeing the rumbling mountain located on the north-east of the holiday island jumped from 48,000 the previous day, as vehicles yesterday delivered more food, face masks and bedding to the evacuees.
President Joko was reported by Agence France-Presse as saying: "It is not easy to handle a volcanic eruption because there is no certainty when it's going to happen, or if it's going to happen at all."
Those evacuated include residents outside the primary evacuation zone, between 9km and 12km from the centre of the volcano.
Officials have said that Bali's tallest volcano, which last erupted about 55 years ago, was at a "critical stage" just before an eruption.
"The (9km to 12km) radius lines, within which residents are recommended to leave, are easy to see on the map, but on the ground it is not that easy. Many of the residents outside the radius who are not sure have opted to also leave," Indonesia's national disaster management agency (BNPB) spokesman, Dr Sutopo Purwo Nugroho, said yesterday.
Bali's capital, Denpasar, its international airport and the tourist magnet Kuta beach are located some 70km away and are safe, but could be affected if a thick ash cloud accompanies the eruption.
Several Singapore-based airlines contacted - Singapore Airlines, Scoot, AirAsia and Jetstar - said their flights were operating normally yesterday, and they are monitoring the situation closely.
Indonesia, which sits on the Pacific Ring of Fire, has 127 active volcanoes, or 13 per cent of the world's volcanoes.
Mount Agung and Mount Sinabung in North Sumatra province are both at the highest alert level - Stage 4 - which means an eruption is imminent.
The rocks blocking the magma are in thick layers inside Mount Agung, thus making it a "strong volcano", according to Indonesian chief volcanologist I Gede Wantika.
"For Mount Agung, an eruption may occur after 2,000 tremors or more a day, while others like Mount Merapi or Mount Kelud, could erupt only after a few tremors a day," he told Jakarta-based Elshinta radio.
BNPB said on Monday that Mount Agung had reached a "critical stage" with about 500 tremors recorded a day compared with just two in previous weeks.
In 1963, its eruption killed 1,549 people and forced 100,000 others to flee their homes.
BNPB's Dr Sutopo had earlier said that if Bali's main Ngurah Rai airport has to be closed, flights will be diverted to nearby airports.
These include those in Semarang, Yogyakarta and Solo in the central part of Indonesia's main island of Java, Surabaya in East Java province and Lombok, an island to the east of Bali.