Evacuation centres and hotels in Bali filled up Tuesday with tens of thousands seeking refuge as a volcano on the Indonesian resort island threatened to erupt, forcing the closure of the main airport for a second day.
Stranded tourists hunted for accommodation while frightened villagers living in Mount Agung's shadow made their way to more than 200 evacuation centres as the mountain gushed smoke and ash.
The rumbling volcano -- which last erupted in 1963 killing around 1,600 people -- forced Indonesian authorities to close Bali's airport for a second day Tuesday as experts raised the alert level to maximum.
Towering columns of thick grey smoke have been rising from the mountain since last week, and in the last few days have begun shooting into the sky, forcing all flights to be grounded until at least Wednesday morning.
Ash is dangerous for planes as it makes runways slippery and can be sucked into their engines.
Officials have warned that the volcano, which looms over the tropical holiday paradise, could erupt at any moment.
Some 40,000 people have abandoned their homes in the danger zone but as many as many as 100,000 will likely be forced to leave, disaster agency officials have said.
"Volcanic ash is still spewing. It's thick and rising very high -- up to three or four kilometres from the crater," said I Gede Suantika, an official at Indonesia's volcanology agency.
The exclusion zone around Agung, which is 75 kilometres from the beachside tourist hub of Kuta, has also been widened to 10 kilometres.
As of Tuesday some 443 flights had been cancelled, affecting more than 120,000 passengers in Bali, a top holiday destination that attracts millions of foreign tourists every year.
Inn operator I Wayan Yastina Joni was among the few hoteliers willing to take up an appeal by Bali's governor and tourism agency to supply free rooms to thousands of out-of-luck visitors, though some offered discounts.
"I don't mind giving free accommodation for tourists I already know," said the owner of the Pondok Denayu Homestay.
"This is nobody's fault. It's a natural disaster that no one expected," he added.
Hundreds of tourists are being shuttled to Indonesia's second city Surabaya, about 13 hours' drive away, so they can fly out of the country.
"We are preparing 10 buses and more can likely be provided later today," Bali Transportation Agency Head Agung Sudarsana said earlier Tuesday.
The airport on nearby Lombok island -- also a popular tourist destination east of Bali -- has opened and closed several times in the past few days. It is currently open but may yet be shuttered again, officials said.
Mount Agung's last eruption in the early sixties was one of the deadliest ever seen in a country with nearly 130 active volcanoes.
"I am very worried because I have experienced this before," 67-year-old evacuee Dewa Gede Subagia, who was a teenager when Agung last roared, told AFP.
"I hope this time I won't have to evacuate for too long. In 1963, I left for four months."
Experts said however that Agung's recent activity matches the build-up to the earlier disaster, which ejected enough debris -- about a billion tonnes -- to lower global average temperatures by 0.2 - 0.3 degrees Celsius for about a year.
"What we are seeing at the moment are small explosions, throwing out hot gases and fragments of molten rock, or ash," said David Pyle, a volcano expert at Oxford University.
"The probability of a large eruption is high, but this may take some days or weeks to unfold."
Agung rumbled back to life in September, forcing the evacuation of 140,000 people living nearby. Its activity decreased in late October and many returned to their homes.
However, on Saturday the mountain sent smoke up into the air for the second time in a week in what volcanologists call a phreatic eruption -- caused by the heating and expansion of groundwater.
Then on Monday so-called cold lava flows appeared -- similar to mud flows and often a prelude to the blazing orange lava of the popular imagination.
Indonesia is the world's most active volcanic region. The archipelago nation with over 17,000 islands lies on the Pacific "Ring of Fire" where tectonic plates collide, causing frequent volcanic and seismic activities.
Last year, seven people were killed after Mt. Sinabung on the western island of Sumatra erupted. A 2014 eruption at Sinabung killed 16.