A powerful earthquake rocked western Indonesia before dawn Thursday, sending panicked residents fleeing from their homes and briefly triggering a tsunami warning.

The quake had a preliminary magnitude of 7.1 and struck 85 miles west of Bengkulu, a coastal town on Sumatra island, the U.S. Geological Survey said. It was centered 18 miles beneath the ocean floor.

The Pacific Tsunami Warning Center and Japan's Meteorological Agency said there was a small possibility it could trigger a destructive tsunami. But the wave never came, and Indonesian authorities later lifted the alert.

There were no reports of damage after the tremor, which struck at 4 a.m., according to Arizal, a local meteorological official, who like many Indonesians goes by only one name.

Residents in Bengkulu — still jittery following a series of powerful quakes that struck the region early last month — fled their homes, el-Shinta radio reported.

Indonesia, the world's largest archipelago with a population of 235 million people, is prone to seismic upheaval because of its location on the "Ring of Fire," an arc of volcanoes and fault lines encircling the Pacific Basin.

A magnitude-9 quake off Sumatra's coast in 2004 triggered a tsunami that killed more than 230,000 people in a dozen countries, most of them in Indonesia.

Last month, an 8.4-magnitude quake off Bengkulu, followed two tremors measuring 7.8 and 7.1, killed 23 people and destroyed thousands of buildings.

The region has since been hit by hundreds of aftershocks. Suhardjono, a senior official at Indonesia's Meteorological and Geophysics Agency, told el-Shinta that Thursday's tremor was among them.

PHOTO CAPTION

A powerful magnitude 7.1 earthquake jolted the Indian Ocean off Indonesia's Sumatra island early on Thursday. [Reuters]

AP