Indonesian scientists Friday downgraded the alert status of Mount Merapi from its highest level after it killed more than 350 people in a series of violent eruptions that started in late October.

"The decision was taken this morning at 9:00 am (0200GMT) as its eruption activities continue to slow down," the head of the volcanology office, Subandrio, told AFP from a monitoring office in Yogyakarta, the main city south of Merapi.

He said that more than 250,000 people who had been living in evacuation shelters were now allowed to return home, except for those who lived in the worst affected district, Sleman, on the southern slope.

"The volcano's threat is now limited to only some parts on the southern slope. People are not allowed to do activities there."

Another volcanologist, Surono, said people must remain away from river banks due to possible fast-moving volcanic mudflow streaming down the volcano's slope during heavy downpours.

"It's especially during the heavy rainfall as the eruptions left an estimated 150 million cubic metres of volcanic material on the slopes," he said.

Hundreds of people fled their houses earlier this week when heavy rainfall flushed thousands of tons of volcanic material into several rivers, damaging a bridge and submerging houses.

Disaster management officials said they had recorded 353 people killed. Many were buried under fast-flowing torrents of boiling hot gas and rock that incinerated villages on the southern slopes when the volcano exploded on November 5, its biggest eruption in over a century.

The volcano, located on the central island of Java, killed around 1,300 people in 1930 but experts say the latest eruptions are its biggest since 1872.