BANDA ACEH, Indonesia (AP) - The U.S. Geological Survey puts the quake's magnitude at 8.6  in the waters of the Indonesian island of Sumatra, and says it was centered 20 miles beneath the ocean floor about 270 from the capital of Aceh province.

The Pacific Tsunami Warning Center in Hawaii issued a tsunami watch for countries across the Indian Ocean, while Indonesia officials issued a tsunami warning for cities along the coast of Sumatra. 

Thailand's National Disaster Warning Center issued an evacuation order to residents in six provinces along the country's west coast.

The shaking lasted for nearly four minutes in Aceh and led to chaos in the streets. Patients poured out of hospitals in several cities, some still attached to IV drips.

There have been several strong aftershocks.