Before holding the fast, the duo visited the Rajghat to offer their prayers to Mahatma Gandhi.
Around 2,000 people have reached the Parliament Street to show their support. According to Delhi Police officials, elaborate arrangements have been made.
Ramdev's Bharat Swabhiman Andolan is also organising sit-ins in various states today.
Today’s protest is likely to see Ramdev announce his strategy with regard to 2014 elections.
The day-long hunger strike comes in the wake of latest allegations leveled against Prime Minister Manmohan Singh and 14 of his cabinet members by Team Anna over allocation of 14 coal blocks to the public and private sector.