(AFP) - Downward-facing dogs, cobras and warriors sprouted all over Asia on Thursday, as the fourth annual International Yoga Day got under way.

Indian Prime Minister Narendra Modi, whose proposal for the global event won UN approval in 2014, led the way, performing his asanas with over 50,000 others in the northern city of Dehradun.

People gathered at a sprawling forest research institute -- snakes and monkeys were removed in advance -- before dawn for the communal session involving the yoga-mad premier, an AFP reporter at the scene said.

"The way to lead a calm, creative & content life is Yoga. It can show the way in defeating tensions and mindless anxiety," Modi said on Twitter.

"Instead of dividing, Yoga unites. Instead of further animosity, Yoga assimilates. Instead of increasing suffering, Yoga heals," the 67-year-old said.

Other gatherings took place in the capital New Delhi with 10,000 enthusiasts registered. Several hundred braved unhealthy pollution levels and hot and humid weather to lay out their mats in the Lodi Gardens park.

At least 5,000 events big and small took place across India, but the largest was expected to be in Mysore in the south with more than 60,000 taking part, according to organisers.

Yoga was also performed on board the Japanese naval ship JS Ise and on the Indian Navy's INS Sahyadri taking part in military exercises in the western Pacific, the Indian Navy said.

Submarine staff from India's Eastern Naval Command were pictured doing yoga poses, as were soldiers in Secunderabad.

Artist Sudarsan Pattnaik created a special sand sculpture with the message "Yoga for Peace and Harmony" on a beach in the eastern city of Puri.

The artwork featured Modi, US President Donald Trump, Chinese leader Xi Jinping, Russian President Vladimir Putin and North Korean leader Kim Jong Un all in the lotus position.

In Tokyo, around 80 people -- mainly in their 60s and 70s -- took part in a special yoga session organised through the Indian Embassy in the Zojoji Temple, the two-storey red shrine in the shadow of Tokyo Tower.

Among those being put through their paces by the guru was a Japanese MP, a member of the yoga group in the Japanese parliament.

Other events were scheduled around the world later, including in Kilkenny in Ireland, Bahrain, Brisbane in Australia and in Milan.

In the Italian city, participants will perform 108 "sun salute" cycles.

On the northern facade of the United Nations building in New York a laser projection of yoga postures has been in place since Monday.

- 'Not to worry' -

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.

He has also spearheaded an initiative to reclaim the discipline as a historic part of Indian culture since his Hindu nationalist government came to power in 2014.

Yoga has boomed in recent decades, with millions practising it regularly, although in the West it is often more of a gymnastic than a spiritual activity.

But this doesn't bother the spiritual head of the biggest ashram or retreat in Rishikesh, the Indian city on the banks of the holy Ganges river considered the world yoga capital.

"At least people are doing it. One day you walk the path, the next day you find the truth also," Swami Chidanand Saraswati told AFP.

"As the Sun is for all, the Moon is for all, rivers are for all, in the same way yoga is for all," he said. "Not to worry!"

© Agence France-Presse