A very strong earthquake of 7.7 magnitude struck in the ocean near India's Nicobar Islands and northwest of the tip of Indonesia's Sumatra island on Saturday, the US Geological Survey said.
A regional tsunami watch was in effect for all areas of the Indian Ocean, the Pacific Tsunami Warning Centre said on its website, listing India, Indonesia, Sri Lanka, Myanmar, Thailand and Malaysia.
"Earthquakes of this size have the potential to generate a destructive local tsunami and sometimes a destructive regional tsunami along coasts" no more than 1 000 km (620 miles) from the earthquake epicentre, the warning centre said.
The epicentre of the quake was 97 miles (155 km) west of Misha on the Nicobar Islands at a depth of 21.7 miles (34 km), USGS said, slightly revising earlier figures.
In December 2004, a magnitude 9.15 quake off the coast of Sumatra triggered an Indian Ocean tsunami that killed around 226 000 people in Indonesia, Sri Lanka, India, Thailand and nine other countries. - Reuters