A day after a false alarm on Indonesia's Mount Kelut led to panic among residents on its slopes, the volcano is showing signs of an imminent eruption, a scientist said Sunday.

"An eruption is now very, very much possible, although so far it has not yet happened," said Agus Budianto, a geologist monitoring the activities of the volcano in the densely populated East Java province.

On Saturday, continuous tremors beneath the volcano became so strong that they could no longer be read on seismological instruments, leading scientists to evacuate their posts and warn an eruption appeared to have occurred.

They could not confirm it visually as the top of the historically deadly mountain was shrouded by clouds but their warning led residents still in the danger zone to flee in fear for their lives.

Budianto said: "There was no lava or ash emitted by the volcano." But the volcano's behaviour on Sunday indicated an eruption was still imminent, he added.

"Besides the rising earthquakes and tremors, we are also witnessing a new phenomenon -- smoke rising from the crater lake and the temperature of the water continuously rising," he told AFP.

A 15-metre (yard) deep lake fills the volcano's crater.

"All these developments show that the volcano has reached some sort of point of no return," he added.

Blitar district spokesman Kamtono said the district chief has issued a written order for the district police to evacuate the few people who have so far refused to leave their homes in the danger zone.

"This step has been taken for the sake of the safety of the people themselves because the risks now appear increasingly higher that an eruption is soon to come," Kamtono said.

About 130,000 people live within a 10-kilometre (six-mile) danger zone around the volcano, officials have said.

Meanwhile, three truckloads of policemen, some armed, were attempting to disperse onlookers watching volcanic debris wash down the mountain.

Experts expect an eruption of Kelut to consist of "heat clouds" or pyroclastic flows of searing gas and volcanic debris rushing down the slopes, similar to the last eruption in 1990 that left 34 people dead.

Since record-keeping began, Mount Kelut's eruptions have claimed more than 15,000 lives, including an estimated 10,000 in a catastrophic 1586 eruption. A 1919 eruption spewed heat clouds that killed 5,160 people.

Indonesia sits on the so-called Pacific "Ring of Fire," where several continental plates collide, causing frequent seismic and volcanic activity.