"Merapi has now entered the eruption phase," a volcanologist at a nearby monitoring post said.

At dawn Monday, the volcano, which has been rumbling for weeks, belched thick, black clouds, sending ash, rocks and volcanic gas as far as four km from its crater toward the Krasak and Boyong rivers south and southwest of the 2,968-metre peak, said Triyani, one of the post''s volcanologists.

The scientists had Saturday raised the alert status at Merapi to its highest level, meaning that an eruption could come soon, and ordered all residents living on the slopes to flee.

Experts warned that residents living within 10 km south and southwest of the crater were in the most danger.

In addition, scientists said the collapse of an unstable lava dome could cause superheated avalanches of lava that reach temperatures of 1,000 degrees Celsius to travel down the mountainsides at high speed.

Many residents still refuse to leave and say that they cannot abandon livestock and fear thieves would arrive if they evacuated to shelters. Many also preferred to follow the advice of local mystics or await the alarm call from the volcano''s traditional "key holder", called Maridjan.

Locals believe 79-year-old Maridjan will receive a message when the volcano is about to erupt - possibly through a dream.

"We will not force them," said Taufik, an official at the coordinating emergency centre in Sleman district. "What we can do is tell them to keep watching the mountain and jump into a waiting vehicle if something unexpected happens."

Most Javanese, who make up the majority of Indonesia''s 220 million people, are Muslims, but many still maintain core animist beliefs. They worship ancient spirits and believe a supernatural kingdom exists on top of Merapi.

Merapi, about 450 km southeast of Jakarta, is one of 65 volcanoes listed as dangerous in Indonesia. Its most deadly eruption took place in 1930 when 1,370 people were killed. It also erupted in 1994, claiming the lives of at least 66.

Indonesia has the world''s highest density of volcanoes, with 500 located in a so-called Ring of Fire in the 5,000 km wide archipelago nation. Of these, 128 are active.

--DPA