WASHINGTON, April 6 (Reuters) - A major earthquake of magnitude 7.8 shook the Indonesian island of Sumatra, the U.S. Geological Survey said on Tuesday.

A local tsunami watch was in effect for Indonesia, the Pacific Tsunami Warning Center said.

The quake was centered 127 miles (204 km) west-northwest of Sibolga, Indonesia, and was at a depth of 28.6 miles (46 km), the USGS said.

It initially reported the quake’s magnitude at 7.6. (Reporting by World Desk Americas))