Thousands of villagers have fled homes lying in the path of red-hot lava flows oozing from Indonesia's Mount Karangetang as the volcano has been put on top alert, officials said Friday. The top alert status means that scientists believe an eruption of the volcano, one of the archipelago nation's most active, could be imminent.

More than 3,900 residents from five villages living around the slopes of the 1,784-meter (5,850 feet) volcano were evacuated Thursday and Friday, said Boy Rompas, a spokesman for the North Sulawesi provincial administration.

Many villagers returned to their homes Friday to tend their fields but were expected back at the shelters at night, Rompas said, adding that local officials would deliver food and medicines to the shelters on Saturday.

Saut Simatupang, a vulcanologist with the national vulcanology monitoring office in West Java, said the top alert status was put in place last Saturday due to increasing flows of lava and heat clouds.

As of Friday, the volcano's lava flows were stretching as far as 1.75 kilometres (one mile) down the volcano's slopes, he said.

"We are continuously monitoring the volcano's activity but fortunately residents there are well-adapted to its activities so they occasionally conduct self-evacuations," he told AFP.

About 16,000 people live in eastern Siau, the area deemed most likely to be affected by any eruption, local officials said.

The volcano is located on Siau Island, about 2,300 kilometres (1,400 miles) northeast of Jakarta and 160 kilometres north of Manado, the capital of North Sulawesi province.

Karangetang is one of Indonesia's most active volcanoes. Six people were killed by lava flow or heat in the volcano's last eruption in May 1992.

Vulcanologists had only earlier this month downgraded the top alert status of another Indonesian volcano.

Mount Merapi, located on the densely populated island of Java, killed two people sheltering in a bunker when it spewed searing clouds of hot gas and ash.