Alerts issued
 
India's government issued a tsunami alert for the Andaman Islands, while in Malaysia people were warned to stay away from beaches.
 
"Earthquakes of this size have the potential to generate a widespread destructive tsunami that can affect coastlines across the entire Indian Ocean Basin," the Pacific Tsunami Warning Centre said.
 
The centre said after the first quake that waves could strike Indonesia and Australia within an hour, with India and Sri Lanka possibly hit within three hours.
 
Sri Lanka also issued an alert for its north, south and eastern districts following the quake, the National Disaster Management Centre said.
 
The alerts were later withdrawn.
 
Indonesia, the world's largest archipelago, is located on the so-called Pacific "Ring of Fire," an arc of volcanoes and fault lines encircling the Pacific Basin, and is prone to earthquakes.
 
In December 2004, a powerful earthquake triggered a tsunami off the coast of Sumatra that killed more than 131,000 people in Indonesia's Aceh province.
 
Nearly one million peple are still struggling to rebuild their communities three years on and thousands remain dependent on outside aid.