Indian Prime Minister Narendra Modi (C) participates in a mass yoga session along with other Indian yoga practitioners (PRAKASH SINGH/AFP/Getty Images)

TENS of thousands of people – from the Himalayan region of Ladakh to the deck of an aircraft carrier – joined India’s Prime Minister Narendra Modi today (21) to celebrate the fourth International Day of Yoga, with a few wearing masks to highlight poor air quality.

Modi pushed for the annual event to be held worldwide after winning power in 2014, with the lifestyle industry centred on the ancient physical and spiritual discipline estimated to be worth around $80 billion.

“Instead of dividing, Yoga unites. Instead of further animosity, Yoga assimilates. Instead of increasing suffering, Yoga heals,” Modi said on Twitter.

Pictures on social media showed participants braved rising mercury levels and unhealthy air quality in some places to spotlight yoga, one of India’s best known exports to the world.

Afghanistan, Japan and Peru held yoga sessions, while Australia and South Africa celebrated on Monday (18).

In India, more than 50,000 people joined Modi in performing yoga in the lawns of Dehradun’s Forest Research Institute, in the Himalayan foothills of the northern state of Uttarakhand.

“From Tokyo to Toronto, from Stockholm to Sao Paulo, yoga has become a positive influence in the lives of millions,” Modi told participants on the lush green lawns.

“In a world where non-communicable diseases, stress and lifestyle-related ailments are rising, yoga can play a central role in mitigating these diseases to create a healthy mind and body.”

Below the surface, photos released by the Indian military showed a submarine crew joining in, while the Air Force tweeted photos of skydiving parachute instructors in yoga poses as they tumbled to earth.

About seven million people die each year from breathing polluted air that can lead to heart disease, stroke and lung cancer, the World Health Organization said in a report last month, most of the deaths happening in Asia and Africa.

India was home to the world’s 14 most polluted cities, with New Delhi, the capital, ranked sixth most polluted, it added.

Delhi’s air quality has improved from the hazardous levels it hit last week, but still ranges around 200 to 400 microgrammes per cubic metre, or roughly three to six times the safe level, government data show.

Some participants wore masks to highlight the alarming quality of the air, which has worsened during recent winters, prompting Modi’s office to directly monitor cleanup measures in New Delhi.

Yoga guru Baba Ramdev led a gathering in Rajasthan, whose chief minister said it was the largest group yoga event.

Troops guarding the world’s highest battleground on the Siachen glacier, in the Ladakh region of northern Jammu and Kashmir state, did yoga routines at an altitude of around 18,000 feet (5,486 m).

The Indian navy also released pictures of sailors doing yoga on board the world’s oldest aircraft carrier, the INS Viraat, decommissioned last year.

Modi is keen on portraying his physical prowess, last week posting on Twitter his morning yoga routine involving plodding around a tree and flexing over a boulder.