Experts warn the enormous volcano Mt Agung on Bali could erupt soon, with the region's leading vulcanologist saying the probability of an eruption is increasing by the day.
The National Disaster Mitigation Agency said about 9400 villagers have been evacuated from their houses to 50 shelters in the districts of Karangasem, Klungkung and Buleleng.
The agency said no residents or tourists should be within 9km of the crater or within 12km to the north, north-east, south-east and south-south-west.
Indonesian authorities raised the alert level for the volcano to the highest level, meaning an eruption could be imminent, the third time in little more than a week that the alert level had been raised.
The volcano has not erupted since 1963, when about 1000 people died.
Seismic monitoring equipment on the volcano recorded 676 tremors on Thursday caused by lava pushing through layers of rock deep beneath the mountain, and in one six-hour period on Friday morning there were another 178 tremors.
Dr Syahbana, the head of volcano mitigation for eastern Indonesia, said the tremors were coming from inside the volcano.
"Our data shows the number of earthquakes is still increasing, which shows that the magma has very huge energy," he said.
"It means we have to be alert to the situation but we don't need to panic."
He said the earthquakes themselves were evidence of the potential eruption.
"Magma is pushing to all directions, finding the softest path," he said.
"At the moment when the magma succeeds to go in a certain path, it creates an earthquake - it opens the path to go to the surface.
The Department of Meteorology, Climate and Geophysics said there has been a "tremendous increase" in the mountain's seismic activity, though it could not give a timeframe.
Australia's Department of Foreign Affairs and Trade said tourists to Bali should reconfirm their trips with their airlines and tour operators.
New Zealand's travel advisory has also been updated from orange to red - level four on a four-level scale - with warnings for the potential for ash clouds to affect flights.
"In the event of volcanic ash clouds, New Zealanders travelling to or from Bali are advised to confirm their travel arrangements with their airline or travel agent directly, prior to travelling to the airport," official advice said.
"If your travel is disrupted, ensure you keep all receipts to support your travel insurance claim."
Flights to Bali were not affected but an exclusion zone around the volcano was already affecting tours and trekking groups.
Dr Syahbana said the 1963 eruption was a 5 on the Volcano Explosivity Index (VEI), far bigger than any recent eruptions in Indonesia. The Mount Sinabung eruptions earlier this year rated only a 2 on the index.
Another Pacific volcano, in Vanuatu, is also threatening to erupt with the country having raised its alert level from three to four - a "moderate eruption state" today - and preparing to evacuate 5000 people.