Indonesia warned yesterday that its most volatile volcano could erupt at any time and started evacuating some of the thousands of villagers living on the mountain's slope.

Mount Merapi has seen increased volcanic activity over the past week and officials have raised the alert level for the 2,968-meter-high mountain to the most urgent level, said government volcanologist Surono, who uses only one name.

The mountain last erupted in 2006, when it sent an avalanche of blistering gases and rock fragments racing down the mountain that killed two people. A similar eruption in 1994 killed 60 people, while 1,300 died in an eruption in 1930.

"Officials have predicted that if it erupts, magma would flow to the southern side," said Sri Purnomo, the head of Sleman District on Java island, where Mount Merapi is located. He said officials were warning some 11,400 villagers living on the mountain's southern slope to prepare for "urgent evacuation." About 40,000 people live close to the mountain.

Purnomo said camps to take in the evacuees were being set up at government buildings and sports fields more than 10 kilometers away.

Hundreds of the elderly and children have been moved from villages near the slopes of Mount Merapi to Umbulharjo village, where they are being placed in government buildings and tents prepared by local officials.

There are more than 129 active volcanoes to watch in Indonesia, which is spread across 17,500 islands and is prone to eruptions and earthquakes because of its location within the so-called "Ring of Fire" - a series of fault lines stretching from the Western Hemisphere through Japan and Southeast Asia.