Japan's Meteorological Agency says it has upgraded the magnitude of Friday's catastrophic earthquake to 9.0.

The agency earlier measured it at 8.8. The quake was already the biggest to hit Japan since record-keeping began in the late 1800s and one of the biggest ever recorded in the world.

The agency warned Sunday of more strong aftershocks following the quake, which unleashed massive tsunamis in northern Japan and killed at least 763 people.

The U.S. Geological Survey has measured the quake at magnitude 8.9, and that number remained unchanged Sunday.