Washington/Tokyo  - An earthquake measuring 7.6 on the Richter Scale struck in the Indian Ocean, prompting the US government to issue a tsunami watch Monday for South and Southeast Asia.

The earthquake was centred about 262 kilometres north of India's Andaman Islands and took place at 1956 GMT, the US Geological Survey (USGS) in Denver, Colorado, reported. It struck in the early Tuesday morning hours local time and was 30 kilometres below the earth's surface.

The Pacific Tsunami Warning Centre in Hawaii issued a tsunami watch for Bangladesh, India, Indonesia, Myanmar and Thailand, saying the earthquake was strong enough to produce a tsunami along coastlines within 1,000 kilometres of its epicentre.

Later, a second earthquake, with a magnitude of 6.6, struck in the Pacific Ocean off the coast of Japan. The quake took place at 2007 GMT, about 170 kilometres southwest of Tokyo, the USGS said. No tsunami watch was issued.

The quake was felt in Japan's central province of Shizuoka, but there were no early reports of damage or injuries. The epicentre was about 20 kilometres below the seabed.

On Sunday, a 6.9-magnitude quake shook Tokyo and surrounding areas.

In December 2004, an earthquake at sea generated a massive tsunami that hit the shores along the Indian Ocean, leaving 230,000 people, mostly in Indonesia, dead. (dpa)