Millions of people across Asia are witnessing a once-in-a-lifetime event - the longest solar eclipse of the 21st century.

The eclipse was first seen in parts of India and China as dawn broke.

Astronomers say the sun will be completely obscured by the moon for about six minutes and 39 seconds at the peak of the eclipse.

People are using special solar viewing glasses and gathering in wide open spaces to view the historic event.  

An eclipse is an astronomical phenomenon when the moon passes between the sun and Earth.

It is not a rare event, but experts say the Earth will not experience an eclipse this long again until 2132.

The eclipse will pass over India, Nepal, Bhutan, Bangladesh, Burma, China, Japan, Indonesia and the Marshall Islands.

Some information for this report was provided by AP.