BANDA ACEH, Indonesia (AP) — A massive earthquake in the waters off the Indonesian island of Sumatra has sent panicked coastal residents across the region fleeing to higher ground.

The U.S. Geological Survey puts the quake's magnitude at 8.6 and says it was centered 20 miles beneath the ocean floor about 270 from the capital of Aceh (AH'-cheh) 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.

Two hours after the quake hit, however, there had been no sign of the feared wave. Damage also appeared to be minimal.