Indonesian officials said more than 120,000 people have evacuated Bali as authorities warned a volcano could erupt in “a matter of hours.”

Nyoman Parwata, an official at the disaster mitigation agency's command post in Bali, said the number of evacuees has swelled to about 122,500.

They are scattered in more than 500 locations across the island famed for its beaches, lush green interior and elegant Hindu culture, taking shelter in temporary camps, sports centers and other public buildings.

The volcano has been at its highest alert level since Friday, sparking the massive exodus of villagers. Thousands of cows are also being evacuated.

The Balinese government has said that the tropical paradise, visted by millions of tourists each year, is safe, but the official advice on the Australian government's travel website says to exercise caution.

An exclusion zone around the mountain extends as far as 7.5 miles from the crater in places but officials say people farther from the volcano are leaving too.

Agung, which dominates the landscape in the northeast of the island, last erupted in 1963, killing more than 1,100 people. It remained active for about a year.

Volcanologists say the recent dramatic escalation in tremors indicates an eruption is more likely than not, but they can't say with certainty when it will happen.

"I would definitely be following the advice to stay outside the exclusion zone," said Heather Handley, an assistant earth sciences professor at Sydney's Macquarie University. The increase in tremors suggests an eruption is "imminent," she said.

Its eruptions in 1963 produced deadly clouds of searing hot ash, gases and rock fragments that traveled down its slopes at great speed. Lava spread for several kilometers and people were also killed by lahars — rivers of water and volcanic debris.

Elsewhere, officials in Vanuatu on Thursday ordered the complete evacuation of an island in the Pacific archipelago where a rumbling, belching volcano is threatening to blow.

Boats will soon ferry residents off Ambae island, which is home to about 11,000 people, in a process expected to take about a week. The Manaro volcano has been increasingly active for a week or more, raising fears of a major eruption.

Indonesia, an archipelago 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.

The Associated Press contributed to this report.