CHANDIGARGH: Indian Prime Minister Narendra Modi called yoga a "people's mass movement" as he took to the mat Tuesday along with millions of others worldwide to celebrate the ancient practice.

Across India, sailors, soldiers, school children and bureaucrats bent and twisted their bodies from early morning at mass outdoor sessions to mark the second International Yoga Day.

Sessions were also held around the world including at the Sydney Opera House where colourful mats were spread outside the Australian landmark, while Afghans and foreigners gathered at the Indian embassy in Kabul.

Yoga-loving Modi, dressed in a white tracksuit, led more than 30,000 people in the northern city of Chandigarh for a mass session where they performed poses and breathing exercises at the outdoor Capitol Complex.

"Do not wait, make yoga a part of your life," Modi urged in a brief speech to mark the event, an idea he successfully asked the United Nations to adopt.

"This is a day linked with good health and now it has become a people's mass movement," the 65-year-old premier said.

Modi took a short break to inspect the poses of his fellow yogis, who included students and soldiers, before returning to his spot.

His ministers were also dispatched to cities around India to stretch and bend alongside school children, while the navy tweeted photos of sailors on mats spread atop an aircraft carrier.

Modi, who credits yoga for his ability to work long hours on little sleep, has been spearheading an initiative to reclaim the practice as an historic part of Indian culture after his Hindu nationalist government came to power in 2014.

Indian scholars believe yoga dates back 5,000 years, based on archaeological evidence of poses found inscribed on stones and references to Yogic teachings in the ancient Hindu scriptures of the Vedas.

Modi, who has established a government ministry charged with promoting yoga, last year led around 35,000 people in New Delhi in an outdoor session to mark the first world yoga day.