Many farmers living within a 5-km (3-mile) radius of the crater have already moved out of the area.

In 1919, the eruption of Mount Kelud sent boiling water down the volcano's slopes, killing 5,000 people in 104 villages.

"Each river in the area has at least seven dams to hamper the flow of lahar (water and rocks). We are very well prepared for this. The dams will help people here feel more secure," said Saut Simatupang, the head of volcano investigation at Indonesia's centre for volcanology and geological hazard mitigation.

He said that barriers along 10 rivers in the area were being strengthened with cement.

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.

Along the street in Mulyorejo district, some people were busy at the weekend making wooden desks for protection.

"Learning from previous experience in 1990 when Kelud last exploded, a lot of people were saved because they hid under the tables," said Sri Kustini, 41.

Some people living on the slopes of the volcano have even put tarpaulins over their roofs in the belief they might provide protection.

"We can just pull the tarpaulin down if the volcano erupts. It will protect us from hot volcanic dust, and hot rocks, even poisonous gas," said Lancur, who lives in Mulyorejo district, on the volcano's slope.