Prime Minister Narendra Modi lead thousands of volunteers today in Dehradun to mark the fourth International Yoga Day celebrations while many union ministers are participating in similar events across the country. Addressing the gathering, PM Modi said, "Yoga has emerged as the biggest unifying force in the world." The Prime Minister reached the venue a little after 6:30 am, he addressed the gathering and is now performing yoga along with those assembled there. PM Modi, who arrived in Dehradun late last evening, was welcomed at the airport by Uttarakhand Governor Krishna Kant Paul, Chief Minister TS Rawat and a host of other leaders and officials.