A massive quake struck on Wednesday off the Indonesian island of Sumatra, a region devastated by the 2004 Indian Ocean quake and tsunami, but initial fears of another region-wide disaster faded as tsunami warnings were cancelled.

Indonesian and Australian authorities called off their tsunami alerts within two hours of the 7.8 magnitude tremor, though it was still unclear if the quake had destroyed any buildings or killed people in Sumatra.

A National Search and Rescue Agency official gave an initial report of some deaths, but later withdrew those comments.

"Up until now, there is no information about deaths," said Heronimus Guru, the agency's deputy head of operations.

Any rescue operation will be hampered by the dark, which falls early in the tropical archipelago.

There were no immediate reports of damage, but the shallower a quake, the more dangerous it is. The U.S. Geological Survey originally put the magnitude at 8.2, revising it down to 7.8.

The epicentre was 808 km (502 miles) southwest of the coastal city of Padang. It was 24 km (15 miles) deep, it said, after first putting its depth at 10 km.

This is a breaking news story. Please check back for further updates.

