India's Prime Minister Narendra Modi (L) and US President Barack Obama watch India's Republic Day parade in the rain together from their review stand in New Delhi, January 26, 2015. [Photo/Agencies]

NEW DELHI - India on Monday began its 66th Republic Day celebrations, with US President Barack Obama as the chief guest at the event.

President Obama, his wife Michelle, Indian President Pranab Mukherjee and Prime Minister Narendra Modi, among other dignitaries and the general public, are watching the Republic Day parade on Rajpath road in front of the presidential palace at the heart of the national capital.

India's military might and cultural diversity are on full display at the parade, amid unprecedented security as the visiting US president, his Indian counterpart and Modi watch the parade from behind a bullet-proof glass enclosure.

Obama is the first US president to be the chief guest at the Republic Day celebrations. He was invited by Modi, an invitation considered as one of the biggest honors India can bestow on a foreign leader.

The Republic Day parade celebrates the adoption of the Indian Constitution in 1950, the day when India became a republic, three years after it gained independence from Britain.