A 7.3-magnitude earthquake struck off the west coast of Indonesia's northern Sumatra early Wednesday, sending panicked residents onto the streets and in search of higher ground.
Thousands on the island of Simeulue, 200 kilometres (124 miles) from the epicentre, ran from their homes as the ground shook, an AFP reporter on the scene said.
But after Indonesia issued a tsunami warning, the residents ran back inside to collect their belongings and then sought higher ground.
A warning was also issued by the Pacific Tsunami Warning Center, but both have since been lifted.
"There were no immediate reports of any damage or casualties, and that's still the case," Meteorology and Geophysics Agency official Tiar Prasetya said.
The agency said the under-sea quake hit at 1:37 am (1837 GMT), while the USGS reported the depth at 29 kilometres (18 miles).
A soldier named Eko who was on the shore on Simeulue when the earthquake struck said he monitored the water levels in fear of another tsunami.
"The water receded about a metre, which is a sign a tsunami is coming. Usually the water rushes back quickly, but that didn't happen, so I was worried a tsunami would hit," he told AFP.
The USGS reported the epicentre was 423 kilometres (262 miles) southwest of Banda Aceh, the capital of Aceh province on Indonesia's Sumatra island.
In Banda Aceh, the ground shook for 30 seconds and terrified residents rushed out of their homes, but they returned indoors shortly after, an AFP reporter there said.
Aceh was the worst-affected area by the December 2004 Indian Ocean tsunami -- triggered by a giant 9.1-magnitude earthquake -- that claimed 220,000 lives, three-quarters of them in Indonesia.
More than 20 people by a river in Banda Aceh climbed a bridge Wednesday morning after the quake to look out for signs of a potential tsunami.
Although the Pacific Tsunami Warning Center dropped its warning, it said: "There is a very small possibility of a local tsunami that could affect coasts located usually no more than a hundred kilometres from the earthquake epicentre."
The Indonesian agency also reported two aftershocks of magnitude 5.4 and 5, respectively about 30 minutes and one hour after the initial quake.
Some coastal residents had moved further inland, taking shelter in mosques or camped by the roadside as a precaution, but there was no sense of panic, the AFP reporter said, adding that the aftershocks were not felt in Banda Aceh.
A powerful earthquake hit Sumatra in September 2009, killing more than 1,000 people, and seismologists have warned of the likelihood of another large quake in the coming years.
Indonesia sits on the Pacific "Ring of Fire", where the meeting of continental plates causes high volcanic and seismic activity.