U.S. officials on Monday reported that a huge 7.6 magnitude earthquake struck in the Indian Ocean and issued a regional tsunami watch for India, Myanmar, Indonesia, Thailand and Bangladesh that was lifted later.

The U.S. Geological Survey said the quake was about 160 miles north of Port Blair in India's Andaman Islands and about 20.6 miles deep.

"The danger for a tsunami is real," William Leith, an earthquake manager at the USGS, said in an interview.

By comparison, however, Leith said that Monday's Indian Ocean quake, though very large, was "many times smaller" than a massive earthquake in December 2004 off Indonesia's western island of Sumatra that triggered a tsunami that killed more than 230,000 people.

The tsunami alert was later lifted.

Also Monday, an earthquake with a preliminary magnitude of 6.6 shook Tokyo and surrounding areas.

Quakes that occur that far apart are typically not related, Leith said, but it was too early to say for sure; he said scientists would be studying the two quakes.

The Indian Ocean earthquake was reported to have struck about 225 miles south-southwest of Myanmar, 510 miles west of Bangkok, and 1,420 miles southeast of New Delhi.