Authorities issued a tsunami alert as a powerful earthquake hit the western coast of Indonesia's Sumatra island.

The quake, with a preliminary magnitude of 6.4, struck nearly 100 miles off the coast of the town of Bengkulu, the Meteorological and Geophysics Agency said.

A series of powerful earthquakes in the same region last month killed 23 people and damaged or destroyed thousands of buildings.

There were no immediate reports of injuries or damage from the quake, which registered at a depth of 12.5 miles.

The US Geological Survey put the quake at a lower magnitude of 6.2.