Indonesian residents living near a rumbling volcano in East Java have begun evacuation drills, officials said Thursday as they warned activity was increasing at the site.

Volcanologists lifted an alert for Mount Kelut to the third of a four-level warning system last Sunday. Hiking the warning to the four level means scientists fear an eruption is imminent.

"The volcano could erupt at anytime... The trend is that there are increasing activities," Saut Situmorang from the vulcanology survey office told AFP, adding however that for now the mountain could still calm.

"We will increase the alert if there are significant signs that the volcano is ready to erupt," he said.

Residents were advised on Sunday to maintain a five-kilometre (three-mile) safety zone around Mount Kelut's crater and were told to prepare to evacuate at the first sign of any eruption.

Officials and volunteers in the district of Nglegok near the volcano were preparing residents and performing drills in case of an eruption, they said.

"Medic teams and youth volunteers performed a drill here yesterday (Wednesday). Many of the residents took part in the simulation," district official Marwoto told AFP.

"We simulated an evacuation, building command posts and also getting (four-wheel drive) cars to difficult locations," he said.

Meanwhile residents in Candisewu village in the district reported sightings of animals such as monkeys, snakes and anteaters fleeing the slopes in past few days.

"Maybe the air near the crater is getting hot, so the animals are running down," resident Mahfud told the state-run Antara news agency.

He said residents had taken it as a sign that they should be prepared for a possible eruption.

The 1,731-metre (5,712-foot) volcano last blew in 1990. It has claimed more than 15,000 lives since 1500, including around 10,000 when it erupted in 1568.

Although Mount Kelut's slopes are sparsely inhabited, the peak is a popular domestic tourist destination and is located on a densely-populated plain.