JAKARTA, March 2 (Reuters) - A powerful and shallow earthquake of magnitude 8.1 struck off the west coast of the Indonesian island of Sumatra on Wednesday, the U.S. Geological Survey said.

The epicentre was 808 km (502 miles) southwest of Padang, USGS said. It was 10 km (six miles) deep.

There were no immediate reports of damage or casualties. (Writing by Nick Macfie; Editing by Clarence Fernandez)

Our Standards: The Thomson Reuters Trust Principles.