Indonesia tsunami death toll hits 311

President Susilo Bambang Yudhoyono was heading to the disaster zone, where fears were growing for hundreds still missing after huge waves triggered by a powerful earthquake Monday hit the Mentawais off the west coast of Sumatra.

Hundreds of kilometres (miles) away, a mass funeral is being held on Thursday for those killed when the nation's most active volcano erupted, the second natural disaster to strike Indonesia in as many days.

Disaster response officials said bodies were being found on beaches and coastal areas in the Mentawais, which took the full force of the tsunami as it washed away entire villages.

"Three hundred and eleven people were killed and 379 are still missing," West Sumatra disaster management official Agus Prayitno said.

Survivors said they had almost no warning that the three-metre (10-foot) wall of water was bearing down on them, despite the laying of a sophisticated network of alarm buoys off the Sumatran coast.

As the magnitude of the disaster became clear, many were asking whether the expensive warning system -- established after the 2004 Asian tsunami which killed at least 168,000 people in Indonesia alone -- had failed.

An official tsunami warning was issued after the 7.7-magnitude quake but it either came too late or did not reach the communities in most danger.

One survivor, 32-year-old farmer Borinte, said the wave slammed into his community on North Pagai island only 10 minutes after residents had felt the quake.

"About 10 minutes after the quake we heard a loud, thunderous sound. We went outside and saw the wave coming. We tried to run away to higher ground but the wave was much quicker than us," he told AFP on Wednesday.

He said he managed to stay alive by clasping to a piece of wood. His wife and three children were killed.

The first images from the scene of the disaster broadcast on Indonesian television showed shell-shocked villagers picking through the sodden ruins of their homes.

"We're still looking for those missing. They could be in the hills, buried by rubble or could have been swept out to sea," West Sumatra provincial disaster management official Ade Edward said Wednesday.

On the central island of Java, rescuers have pulled the bodies of at least 32 people from a tomb of fine grey ash after Mount Merapi erupted on Tuesday, including the elderly spiritual gatekeeper of the "Mountain of Fire".

Officials said almost 42,000 people had fled to cramped temporary shelters around the nearby city of Yogyakarta, but there were fears for the fate of thousands more who had refused to budge.

Soaring above the rice paddies of central Java, the 2,914-metre (9,616-foot) Mount Merapi is the most active of the 69 volcanoes with histories of eruptions in Indonesia. It last erupted in June 2006, killing two people.

The United States and several of Indonesia's neighbours have pledged help for a nation which often finds itself battling calamity, although Jakarta said it did not see a need for foreign assistance.

The Vatican also appealed to the international community for aid.

The tsunami surged as far as 600 metres inland on South Pagai island, officials said. On North Pagai, a resort and almost 200 houses were flattened.

Medical personnel flew in on helicopters but rescue efforts have been hampered by bad weather and poor communications to the islands, which are about half a day's ferry ride away from the port of Padang on Sumatra.

Troops and naval personnel were also dispatched to the area. Indonesian western fleet commander Marsetio said at least five warships were on their way.

US President Barack Obama, who lived in Indonesia as a boy and is due to return there on an Asian tour next month, voiced his sadness over the deaths and pledged US help.

Indonesia straddles a region where the meeting of continental plates causes high seismic activity. It has the world's largest number of active volcanoes and is shaken by thousands of earthquakes every year.

A 7.6-magnitude earthquake last year in Padang killed about 1,100 people, while the 2004 Asian tsunami -- triggered by a 9.3-magnitude quake along the same faultline -- killed at least 168,000 people in Indonesia alone.