New Delhi: Delhi police have registered a case against unknown persons for defacing boundary walls by pasting posters of Prime Minister Narendra Modi that carry the tagline "The Lie Lama".

Police teams have fanned out across several neighbourhoods to try and zero in on those who had stuck the posters, whose images went viral on social media on Thursday afternoon.

Officers said they had acted on a complaint but would not reveal who the complainant was.

The posters, showing a smiling Modi with his hands folded, come at a time the Prime Minister has been accused of making untrue remarks during the Karnataka election campaign, which ended on Thursday.

On Wednesday, Modi had alleged that Congress leaders had not visited freedom fighters Bhagat Singh and Batukeshwar Dutt in jail. The Congress replied by citing historical documents that refer to Jawaharlal Nehru and other senior party leaders visiting Bhagat Singh in prison.

"Go and read history before misusing it for politics. Nehru not only met them in prison but also wrote about them. Several Congress leaders defied Gandhi to speak for them," historian S. Irfan Habib, an expert on Bhagat Singh, had tweeted after Modi's claim.

A senior IPS officer posted at Delhi police's headquarters said: "After learning that such posters had been plastered on a wall in Mandir Marg near Connaught Place and two other places, we immediately alerted our police team."

PCR vans removed the posters, including some pasted at central Delhi's Patel Nagar and Shanker Road areas.

"A case was registered last night under the Delhi Prevention of Defacement of Property Act against unknown persons," the officer said.

An officer at Mandir Marg police station said that several residents had been questioned but none had yet confirmed seeing anyone pasting the posters. The police, he added, were scanning CCTV cameras.

The police's action contrasts with their treatment of Wednesday's defacement of a road sign featuring the Mughal emperor Akbar's name.

A man named Milan Som, who described himself as "divisional convener" of the Bajrang Dal's Meerut unit, has claimed responsibility.

The group had pasted on the signage a sticker carrying the name of Maharana Pratap, who had fought Akbar, on the Rajput king's 478th birth anniversary.

The sticker was removed and the police registered an FIR under the property defacement law but are yet to make any arrests despite the perpetrators being known. Defacement carries a maximum jail term of a year and a fine of Rs 5,000.

Asked why the Bajrang Dal supporters who had been identified for defacing the Akbar Road signage have not been arrested yet, a senior Delhi police officer said: "Our men have not be able to tack them down."

An officer of Tilak Marg police station, where the FIR was registered for defacing the signage, said: "It's a political issue and unless we get an order from the top, there is no question of making any arrest in the case."