|Dozens of people are still missing a day after an earthquake triggered a tsunami that struck western Sumatra [EPA]
Dozens of people have been killed in a tsunami triggered by a powerful earthquake that struck off the western Indonesian island of Sumatra late on Monday.
On Tuesday a health ministry official said that 113 people had died and 500 more were missing.
Agolo Suparto, a spokesman with Indonesia's Disaster Management Agency, said 10 villages were swept away by the tsunami and the number of deaths is likely to rise in the coming days.
The 7.7 magnitude undersea earthquake struck near the Mentawai island chain which lies to the west of Padang on Sumatra.
The quake hit at 9:42 pm (14:42 GMT) at a depth of 20.6km, 280 km south of Padang, the US Geological Survey said.
"A significant tsunami was generated by this earthquake," said the Pacific Tsunami Warning Centre.
The first tremor was followed by strong magnitude 6.1 and 6.2 aftershocks several hours later, sending hundreds of residents fleeing to higher ground.
Details of the damage and casualties came in late because it took 12 hours for rescue teams to reach the remote islands.
The tsunami destroyed at least one boat, with another reported missing with 13 people onboard, including a group of Australian tourists.
"We felt a bit of a shake underneath the boat... then within several minutes we heard an almighty roar," said Rick Hallet, an Australian who operates a boat-chartering business in Sumatra.
"I immediately thought of a tsunami and looked out to sea and that's when we saw the wall of white water coming at us."
Mudjiharto, the head of the Indonesian health ministry's crisis centre, said a three-metre-high wave washed away hundreds of houses in two coastal villages in the island chain.
"Eighty per cent of buildings in Muntei village have been damaged by the waves and many people are missing there," said Mudjiharto, who like many Indonesians goes by only one name.
Mudjiharto said medical personnel were on their way to the most devastated areas in helicopters but rescue efforts have been hampered by disruption to communications in the area.
Andrew Judge, chief executive officer of Surfaid International which helps local communities in Sumatra, told Al Jazeera that reports of deaths and damage are escalating.
"The devastation has only been revealed to us this afternoon, so we are moving as quickly as we can.
"There is only one airfield in the Muntei, an old military base, that is used. There is scope to land a helicopter.
"We are working closely with the Indonesian government and our contacts in the surf industry to find out the scope and what needs to be delivered.
"Our worries are not only with the deaths and missing, but also the evacuation site, health and hygiene, and nutrition.
"If people are suffering from malaria or are malnourished particularly the very young or very old, and they are moved away from their homes, we are worried about disease outbreaks and further deaths in the weeks to come."
The Asian tsunami in December 2004 - triggered by a 9.3-magnitude quake off northwest Sumatra - killed at least 168,000 people in Indonesia alone.