A strong earthquake measuring 7.8 magnitude on the Richter scale hit near Nicobar Islands, India early Sunday local time, the United States Geological Survey reported, and a tsunami warning was issued for all areas of the Indian Ocean by the Pacific Tsunami Warning Center (PTWC).

The powerful earthquake occurred at 1:26 a.m. on Sunday local time (1926 GMT on Saturday). The epicenter was some 150 km west of Mohean, Nicobar Islands, close to Indonesia's Banda Aceh, with a distance of 440 km. The depth of the epicenter is 35 km.

Following the quake, the PTWC issued its tsunami warning, and a tsunami watch is in effect for India, Indonesia, Sri Lanka, Myanmar, Thailand and Malaysia.

The center later downgraded the watch, saying only India is at risk.

In its evaluation, the PTWC says an earthquake this size has the potential to generate a destructive local tsunami and sometimes a destructive regional tsunami along coasts located usually no more than 1,000 km from the epicenter. Areas further than that could experience small sea level changes and strong or unusual coastal currents.

The Indian Ocean's coasts were hit by a huge tsunami in 2004, in which hundreds of thousands perished.