(Reuters) - An earthquake with a magnitude of 7.0 struck off the southwest coast of Alaska late on Thursday, the U.S. Geological Survey reported.

The USGS said the quake's epicenter was 104 km (64 miles) south-southeast of Ugashik and 61.7 km deep. The agency upgraded the temblor to a 7.0 after initially stating it was slightly weaker.

The Pacific Tsunami Warning Center said that based on its available data, no tsunami was expected.

The USGS said the quake was unlikely to cause casualties and notable damage, and there were no immediate reports of such.

The area near the quake, centered some 400 miles (643 km) southwest of Anchorage, is lightly populated, according to the USGS.

(Reporting by John Stonestreet in London and Curtis Skinner in San Francisco; Editing by Mark Heinrich)