Red-hot lava which had blazed a trail only 200 metres (yards) down Merapi's slopes by Wednesday had reached 1,500 metres down the southern slope, the office monitoring the volcano said in its daily report.

"I ask that immediate safety steps are taken, beginning by taking at least 50 percent of the total population from the danger zone down," he was quoted as saying by the state-run Antara news agency.

The vice president, who toured the volcano's slopes and met with ministers and local leaders there holding preparatory talks ahead of an anticipated eruption, said that about 34,000 people were in the current danger zone.

"In Magelang, around 15,000 people should be evacuated in one or two days, while (the evacuation) is already progressing in Sleman," Kalla said, referring to the two districts the zone covers.

Kalla, who also heads the National Disaster Agency's coordination board, said that an eruption of Merapi was only a matter of time but gave no forecast and the alert status remained one level below that requiring mandatory evacuation.

The volcanology office in Yogyakarta, 30 kilometres (18.5 miles) south of Merapi, said that besides the increased lava flow, Merapi was still shooting clouds of smoke 600 meters (yards) into the air.

A new lava dome has been rapidly forming at the peak of Mount Merapi. Scientists have said that its collapse will send lava as well as deadly heatclouds speeding down its slopes rather than a massive explosion.

Merapi's most deadly eruption occurred in 1930, when 1,369 people were killed.

Indonesia sits on the Pacific "Ring of Fire" noted for its volcanic and seismic activity. The country has more than 100 active volcanoes.

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