Indonesian authorities have raised the alert level for the Mount Agung volcano on the tourist island of Bali to the highest level, and more than 11,000 villagers have left their homes around the mountain, officials said.
Some 10,000 villagers have already left their homes around the mountain, while more than 200,000 have received warnings.
The Ministry of Foreign Affairs and Trade in New Zealand said 410 New Zealanders have registered on its safetravel.govt.nz website as being Indonesia and it is advising other Kiwis also in the region to also sign up.
Residents and tourists have been warned to stay at least 6km from the crater.
MFAT has also warned there could be flight disruptions due to volcanic ash clouds and New Zealanders travelling to and from Bali should confirm their travel arrangements with their airline or agent before heading to the airport.
It was the third time in little more than a week that the alert level was raised. The Department of Meteorology, Climate and Geophysics said there has been a "tremendous increase" in the mountain's seismic activity, indicating a greater probability of an eruption, though it couldn't give a timeframe.
The Volcano Observatory Notice for Aviation reports the volcano's seismic activity had dramatically increased. "This number of seismicity is an unprecedented seismic observation at Agung volcano ever recorded by our seismic networks," it said in a statement.
Earlier, the Department of Meteorology, Climate and Geophysics said in a statement there has been a "tremendous increase" in seismic activity at the mountain, indicating a greater probability of an eruption.
Indonesia's National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said overnight that the hazardous zone had been increased from 9km to 12km, covering an area encompassing about 240,000 people and prompting further evacuations. He urged people to "calm down" and seek reliable information.
"Estimated danger zones are dynamic and are being continuously evaluated. (They) are subject to change at any time following the most recent observation data," Indonesia's volcano observation authority warned.
'Killer' volcano
Indonesia's volcano monitoring body, Magma, warns Mount Agung's eruptions are characteristically explosive and effusive - resulting in deadly pyroclastic flows of ash, rock and lava.
"In case of eruption, the potential primary hazard that may occur within a radius of 9km is pyroclastic fall of size equal to or greater than 6cm," its website on Agung reads.
But its modelling for some of the terrain around the volcano also shows such flows could cover 10km in less than 3 minutes.
"If an eruption occurs, there is considerable disaster potential," it warns. "People around Mount Agung also do not have enough experience to face the eruption because this volcano last erupted ... 54 years ago."
Agung last erupted in 1963, unleashing deadly pyroclastic flows which killed about 1100 people and hurling ash as high as 10km.
It is just one of 130 active volcanoes in Indonesia, part of the Pacific "Ring of Fire" convergence of tectonic plates.
Warga Kec Rendang Kab Karangasem evakuasi mandiri ke Kota Klungkung pasca ditetapkan status Awas Gunung Agung. pic.twitter.com/21bRFkNPsw
The National Disaster Mitigation Agency earlier said no residents or tourists should be within 9km of the crater and within 12km to the north, northeast, southeast and south-southwest. The volcano is about 70km from the tourist hub of Kuta.
The agency earlier said about 9400 villagers have evacuated from their houses and are scattered across the districts of Karangasem, Klungkung and Buleleng.
They are living in temporary shelters, sports centres, village halls and with relatives, said agency spokesman Sutopo Purwo Nugroho.
More than 7000 of the evacuees were in the 840sq km district surrounding the volcano, Karangasem, which is home to about 408,000 people.
Travel warning
The Australian Department of Foreign Affairs issued an updated travel warning for Indonesia that said an eruption could impact air travel in the region.
"Contact your airline or tour operator to confirm travel plans," it said.
It also warned Australians to monitor local media and follow the instructions of local authorities.
The mountain, 72km to the northeast of the tourist hotspot of Kuta, is among more than 120 active volcanoes in Indonesia. The country of thousands of islands is prone to seismic upheaval due to its location on the Pacific "Ring of Fire," an arc of volcanoes and fault lines encircling the Pacific Basin.