The country's volcanological survey raised Mount Kelud's alert status to the second-highest level on Sunday, following increased activity.
A mix of carbon dioxide and toxic substances seven times normal levels has been recorded from the volcano in recent days, prompting authorities to isolate the area, said Saut Simatupang, head of the survey's volcano observation unit.
"We have advised everyone to stay away within a radius of 5 km (3 miles) from the volcano in anticipation of an eruption that could take place any moment," Simatupang told Reuters.
"We have reason to believe that the magma is very close to the crater's surface."
About 100,000 people, mostly farmers, live on the slopes of Mount Kelud which lies about 90 km (55 miles) southwest of Surabaya, Indonesia's second-largest city.
Many people in villages nearest to the crater, located on the borders of the safe zone, have already left their homes, local rescue official Dedi Sandriya told Reuters.
"Yes, we are afraid. But amid the fear we are prepared to leave, to save ourselves and save the people," Sandriya said.
Plantation worker Turmudi, like many of his fellow villagers, keeps a cardboard box with important survival items at his bedside. He is ready to leave anytime.
"I have already sent my family to live with my relatives in another town. Personally, I am afraid to stay the night," said Turmudi, who like most Indonesians goes by one name. But both Sandriya and Simatupang said official evacuation would not take place until the 1,731-metre (5,712-foot) volcano's alert status is raised to the maximum.
"Once there are stronger, more frequent tremors we will raise Mount Kelud's alert status," Simatupamg said from his office in Bandung.
A 1919 eruption of Mount Kelud caused the lake in its crater to burst through the volcano rim and sent boiling water down its slopes, killing 5,000 people in 104 villages.
Indonesia has the highest number of active volcanoes of any country, sitting on a belt of intense seismic activity known as the "Pacific Ring of Fire.
Last Mod: 04 Ekim 2007, 11:41