Demonstrators across India protested Lankesh's murder. Photo: AFP

An online campaign was launched against Indian Prime Minister Narendra Modi after it surfaced that he is following Twitter account users who appeared to celebrate and justify the recent murder of a prominent Indian journalist, AlJazeera reported. 

Editor of the weekly Gauri Lankesh Patrike publication, Gauri Lankesh, was shot dead by unidentified attackers outside her house in Bangalore on Tuesday.

#BlockNarendraModi was the top trend in the country on Wednesday night through to Thursday, with users demanding that Modi un-follow the handles and apologise.

Modi has yet to condemn Lankesh's death.

Journalists, politicians, and activists across India sharply denounced the murder.

Indian users decided to block the premier after it surfaced that many of the trolls were followed by leaders of the ruling Bharatiya Janata Party (BJP), including several claiming Modi as their follower.

One of the tweets celebrating Lankesh?s murder was sent by user Ashish Mishra, who wrote in response to a news story about the journalist?s death: jaisi karni vaisi bharni (you reap what you sow).

Another Twitter account followed by Modi, Nikhil Dadhich, equated Gauri, an outspoken critic of right-wing groups, to a "bitch". His tweet, written in the Hindi language, was apparently deleted later. Its closest translation reads as: "It took a bitch to die a dog's death, for all pups to howl in the same tune".

Many Indians registered their anger by blocking Modi, who is one of the most popular world leaders on Twitter with 33.8 million followers.

Several groups, including the Committee to Protect Journalists (CPJ), have demanded a thorough investigation into the killing, while a Special Investigating Team has been tasked with probing the murder.

The comments against Lankesh drew the attention of Ravi Shankar Prasad, minister of law and justice and of information technology, who condemned the trolls, many of them ruling party supporters, for expressing happiness at the killing of the journalist.

The ruling Bharatiya Janata Party (BJP), however, defended Modi for following trolls.

Amit Malviya, BJP's head of IT Cell, refused to comment on the issue but referred Al Jazeera to a party statement released on Thursday that dubbed the controversy as "mischievous and contorted".

"PM Modi is the only leader who freely engages with people on social media platforms," the statement said.

"The PM following someone is not a character certificate of a person and is not in anyway a guarantee of how a person would conduct himself."