The Indonesian island of Sumatra has been hit by at least two strong earthquakes, and several aftershocks.
Several people have been killed and injured and officials fear bad communications could be hiding the scale of the impact.
When the first earthquake hit on Wednesday, buildings collapsed, sending panicked residents onto the streets.
Hundreds of miles away in the capital, Jakarta, office buildings swayed, spreading fear among office workers.
US seismologists described the 8.4-magnitude earthquake as the strongest recorded anywhere this year.
The second quake, registering a magnitude of 7.7, hit as the government was arranging relief supplies and sending assessment teams to the area.
Tsunami warnings were repeatedly issued and lifted around the Indian Ocean, spreading panic in many countries in the region.