Strong earthquakes have struck off the coasts of India and Japan, prompting tsunami warnings in both regions.

An earthquake measuring 7.6 on the Richter scale has struck in the Indian Ocean off India's Andaman Islands.

The quake has triggered a tsunami watch for India, Burma (Myanmar), Indonesia, Thailand and Bangladesh.

The US Geological Survey said the earthquake, initially reported as a magnitude 7.7, was 33km deep and was centred 260km north of Port Blair in the Andaman Islands.

Indonesian authorities said they are monitoring the situation.

The Andaman Islands were badly hit by the 2004 Asian tsunami, which was caused by an earthquake off the Indonesian island of Sumatra and sent giant waves crashing into countries around the Indian Ocean.

Houses rattle in Japanese capital

Elsewhere, a strong earthquake with a magnitude of 6.6 has hit eastern and central Japan and rattled houses in Tokyo.

The quake, which struck at 5.07am (9.07pm Irish time), prompted a tsunami warning for waves of up to 50cm for parts of the Pacific coast, the Japan Meteorological Agency said.

A motorway has been closed and a nuclear power station at Hamaoka has shut two units for safety checks.

The focus of the tremor was 20km deep under Shizuoka prefecture and around 150km southwest of Tokyo.