MOSCOW, October 1 (RIA Novosti) - The death toll from two earthquakes that hit Indonesia's Sumatra island this week has risen to 770, with about 2,400 injured, officials said on Thursday.

Western Indonesia has suffered two major quakes in the past two days. On Wednesday, a quake with magnitude of 7.6 struck West Sumatra's regional centre of Padang, destroying 75% of buildings and killing hundreds of people.

On Thursday morning, a second quake measuring 6.9 hit Sumatra island.

Earlier on Thursday, Health Minister Siti Fadillah Supari said the number of fatalities could reach several thousand.

Russia's emergencies ministry earlier said it would send rescue workers, doctors and a mobile hospital to Indonesia to help in rescue work.

The disasters are the latest in a spate of natural and man-made calamities to hit Indonesia.

Part of the Pacific's Ring of Fire, Indonesia is in the world's most seismically active region, registering 6,000-7,000 earthquakes with a magnitude of 4.0 or above annually.

On Wednesday, an earthquake thousands of kilometers to the west caused several tsunamis, which hit the Pacific island nations of American and Western Samoa, and Tonga, killing hundreds of people.