A powerful 7.5-magnitude earthquake struck off the Indonesian island of Sulawesi on Monday, killing four people, toppling homes and triggering tsunami warnings that sparked widespread panic.
Thousands of people fled to higher ground in the middle of the night after US and Indonesian agencies warned of a possible tsunami in the minutes after the quake struck, reported AFP.
"Some residents saw an abnormal sea level as high as two metres (six feet). They thought that a tsunami would strike in a matter of minutes," said Nasir Maroto, a council member in worst-hit Buol district of Central Sulawesi.
The US Geological Survey (USGS) said the shallow earthquake struck 136 kilometres (84 miles) off the coastal town of Gorontalo.
US and Indonesian authorities immediately warned that the quake was strong enough to cause a devastating tsunami but there was no killer wave and the Indonesian warning was withdrawn shortly after being issued.
Indonesia was the country worst hit by the earthquake-triggered tsunami in December 2004 that killed more than 200,000 people in 11 nations across Asia, including over 168,000 people in Indonesia's Aceh province alone.
Officials in Buol district, about 600 kilometres north of the Central Sulawesi capital of Palu, said at least three people had died in the area and about 700 houses had collapsed.
"A collapsing wall and roof hit them as they were trying to escape," local official Syamsuddin Mangge told AFP. He said another 20 people had been hospitalised with injuries.
A 56-year-old man was killed and 23 people were injured in Kwandang village, Gorontalo province, an Indonesian crisis centre official said.
Central Sulawesi governor HB Paliuju said communications with Buol had been cut in the quake and information was sketchy.
An official also said people of Tolitoli district of Central Sulawesi had so reported collapsed buildings but no fatalities.
The Hawaii-based Pacific Tsunami Warning Center warned that the quake had the potential to spawn a destructive regional tsunami and advised authorities in the region to "take immediate action to evacuate coastal areas."
There were at least three powerful aftershocks with magnitudes of up to 6.0, according to Indonesian monitors.
The Indonesian archipelago straddles several continental plates in an area known as the Pacific Ring of Fire, where seismic and volcanic activity is recorded on an almost daily basis.
Monday's quake came less than a week after Indonesia launched a high-tech tsunami warning system in a bid to prevent a repeat of tragedies like that in 2004.
The 1.4 trillion rupiah (130.2 million dollar) system is able to detect an earthquake at sea and predict within five minutes whether it could cause a tsunami.
The system, built with German technology and funding from a number of foreign nations, will eventually include 23 or 24 buoys linked by cables to detectors on the ocean floor.
President Susilo Bambang Yudhoyono said at the launch Tuesday that Indonesia was "living on the edge."
"Three tectonic plates -- the Eurasian, Indo-Australian and Pacific -- meet here," Yudhoyono said.
"This kind of disaster can strike at any time."