Muhammad Bilal Khan, having over 16,000 followers on Twitter, 48,000 on his YouTube channel and 22,000 on Facebook, was with his uncle Ehtesham, when he received a phone call after which a man took him to the nearby forest on Sunday night, Dawn news quoted police as saying.
Superintendent of Police Saddar Malik Naeem said Khan was attacked in the G-9/4 area of Islamabad and was shifted to a hospital where he succumbed to his injuries. His uncle was severely injured and has been hospitalised, he said.
The suspect used a dagger to kill him, Naeem said, adding that some people heard gunshot firing as well.
Apart from being a social media activist, Khan was also a freelance journalist.
He hailed from Gilgit-Baltistan and was a Shariah graduate from the International Islamic University of Islamabad (IIUI), according to Express News.
Soon after his killing, #Justice4MuhammadBilalKhan started trending on social media.
Several Twitter users said that his criticism of the Pakistan Army and the Inter-Services Intelligence (ISI) led to his killing.
"Pakistani activist and journalist Mohammad Bilal Khan was shot dead last night in Islamabad. Khan was known for his criticism of the all-powerful military and its notorious spy agency," a man said in a tweet.
The deceased's father Abdullah said that his body had marks of a sharp tool.
"My son's only fault was that he spoke about the Prophet," he said.
A case was registered under various sections including the Anti Terrorism Act.
The incident has created fear among people, Khan's father said.
Ajay Lalvani, a reporter with a private Royal News TV channel and an Urdu language newspaper Daily Puchano, died on Thursday after he sustained bullet injuries in stomach, arm and knee.
He was sitting in the barber shop in Sukkur city when assailants on two bikes and a car drove by and opened fire.
Lalvani was rushed to a nearby hospital where he died.
His father Dileep Kumar said that the family did not have any enmity, dismissing the police's claim of the murder being the result of a personal enmity, according to The News International.
Condemning the killing, Hindu member of Pakistan's National Assembly (MNA) Lal Chand Malhi said that it is a matter of great concern .
Strongly condemn D killing of yet another journalist Ajay Kumar at Saleh Pat, Sindh. It is a matter of great concern that media persons are increasingly feeling unsafe in Sindh. Offered condolence to the heirs of the victim. Police should (go) beyond forming comtes. (sic), he said on Twitter.
A group of journalists, holding the police responsible for the incident, protested against Lalvani's killing and carried out a march, claiming that it was a targeted killing.
Lalvani's body was cremated amidst tension in Sukkur city which remained shut on the second consecutive day, the police said.
Journalists, many of whom from Karachi, Khairpur, Shikarpur, Larkana, Sukkur and other towns, participated in the last rites along with Lalvani's relatives, friends and members of the minority Hindu community, Dawn newspaper reported.
The police said that they were investigating the motive of crime, and if it was linked with the victim's professional responsibilities.
Pakistan ranks ninth on the Committee to Protect Journalists' annual Global Impunity Index, which assesses countries where journalists are murdered regularly and their killers go free.
Meanwhile, New York-based Committee to Protect Journalists (CPJ), an American independent non-profit organisation, urged authorities in Sindh province to must immediately launch a credible investigation and apprehend those responsible for the killing.
Hindus form the biggest minority community in Pakistan. According to official estimates, 75 lakh Hindus live in Pakistan. However, according to the community, over 90 lakh Hindus are living in the country.
The majority of Pakistan's Hindu population is settled in Sindh province where they share culture, traditions and language with Muslim residents.