At least 100 people have died and scores missing after a tsunami was triggered by a powerful earthquake off Indonesia.

The 7.7-magnitude earthquake struck in the Mentawai Islands area west of Sumatra late on Monday, generating waves as high as three metres which swept away ten villages.

Head of the Health Ministry Crisis Centre Mudjiharto said the Mentawai waves reached up to three metres high and waters swept as far as 600 metres inland on South Pagai island, which was hardest hit. Medics are on their way to the most devastated areas in helicopters but rescue efforts have been hampered by disruption to communications in the area.

Rescuers have also launched a search for a boat believed to be carrying a group of nine Australians and a Japanese national that has been missing since the quake.

Indonesia is located on the Pacific "Ring of Fire" where the meeting of continental plates causes high volcanic and seismic activity and the archipelago is frequently struck by powerful earthquakes.

The 2004 Asian tsunami - triggered by a 9.3-magnitude quake off Sumatra - killed at least 168,000 people in Indonesia alone.