With 6.8 million followers, Prime Minister Narendra Modi has become the world's most followed leader on Facebook's photo-sharing app Instagram, a new study revealed on Wednesday.

Modi, who was at third spot on Instagram last year, is closely followed by the US President Donald Trump with 6.3 million followers, said the study conducted by global public relations firm Burson-Marsteller.

The study looked at the activity of the 325 Instagram accounts of heads of state and government, and foreign ministers over the past 12 months.

Though Modi has only 53 photos posted on his account, he has been termed as the most effective world leader on the photo-sharing app, considering that each of his posts receives an average of 223,000 interactions.

"Leaders around the world are creating online communications that convey global social and political context while also sharing a sense of personality and creativity. Leaders of business and all other sectors can learn from governments' use of Instagram," said Don Baer, CEO of Burson-Marsteller, in a statement.

At third place is Pope Francis with 3.7 million followers, a place ahead of the White House account that has 3.4 million followers.

With a whopping 673 per cent growth in his followers over the past 12 months, Indonesia's President Joko Widodo occupies the fifth position with 3.4 million followers.

In terms of average interactions per post, Turkey's President Recep Tayyip Erdogan holds the second position with 141,000 interactions while Pope Francis' Instagram posts receive 138,000 interactions on average.

"As of April 1, 2017, the accounts have a combined total of 48.7 million followers and published 61,281 posts in the past 12 months which have garnered a total of 371.7 million interactions," the report noted.

All the photos posted on the White House Instagram account set up under Obama in 2012 were archived on the @ObamaWhiteHouse Instagram account on January 20 this year.