As Rahul Gandhi trekked across India on a march that even critics say has improved his image, the descendant of three past premiers was followed all the way by online disinformation.

For Gandhi's opposition Congress party, the main source of this barrage of lies and doctored videos is the well-oiled social media army of Prime Minister Narendra Modi's ruling Bharatiya Janata Party (BJP).

Gandhi, 52, is due to end his 3,500-kilometre (2,175-mile) journey next week, but the trek has attracted little attention from mainstream Indian media. Online, it has been smeared with disinformation.

The false claims have included saying the flag of India's archrival Pakistan was raised during the march, and that Congress workers distributed cash to attract attendees.

One video showed Gandhi enjoying a sexually explicit song -- India remains deeply conservative -- but the audio was doctored, with the original song from a Bollywood movie.

Another image was digitally altered to show Gandhi having alcohol served at his table, an implied moral laxity aimed at hurting his standing among devout Hindus and Muslims.

- BJP 'rattled' -
Fact-checking organisations in India, including AFP, have published nearly 30 blogs debunking false claims about the march that appeared on Facebook, Twitter and instant messaging platforms.

Congress, which ruled India for decades but now looks like a spent force, has pointed the finger at the BJP for attempting to mock and discredit Gandhi.

Supriya Shrinate, chairperson of Congress's social and digital media team, said the BJP has put out at least 10-15 "big lies", including on what Gandhi wore, ate and how he worshipped.

"BJP is completely rattled... This is not the first time they have maligned the image of Gandhi, and they will do it again. This is a well-crafted machinery that along with big media and corporates are targeting him," she told AFP.

Some of the false claims have come from senior figures within the BJP.

Amit Malviya, in charge of BJP's National Information and Technology Department, shared a clip on Twitter alongside a false claim that a senior Congress member was tying Gandhi's shoelaces.

"The arrogant entitled brat instead of helping himself is seen patting his back," Malviya wrote in the tweet, viewed 1.1 million times and which Twitter labelled as "presented out of context".

Congress's own social media team tweeted a video statement from the Congress politician in the video explaining that he was tying his own laces, not Gandhi's. This was viewed just 160,100 times.

- Polarisation -
Neither Malviya nor BJP spokesperson GVL Narasimha Rao responded to requests for comment from AFP on this story.

Online disinformation has exploded in India, alongside mushrooming cellphone ownership and internet usage in recent years.

While all political parties, including Congress, are guilty, the BJP and its social media team are by far the most prolific, experts say.

Joyojeet Pal, an associate professor at the School of Information at the University of Michigan, was sceptical about how much fact-checking and debunking disinformation can help.

"With the level of polarisation we see in India right now, people will believe or at least pretend to believe what better suits their predispositions than what is fact."