According to a report in The Telegraph, Ehsanullah Ehsan, spokesperson for the Jamaat-ul-Ahrar militant group, had 69 connections on LinkedIn, which indicated a sizeable network.
Ehsan did not hide his associations and openly promoted himself on the social media site as the spokesperson for the Jamaat-ul-Ahrar.
He described himself as "self-employed" and even listed his skills as "jihad and journalism", while providing details of his school, employment history and language skills. He also posted his photograph on the site.
The Jamaat-ul-Ahrar militant group split from the Tehreek-e-Taliban Pakistan (TTP) in August 2014. Ehsan is widely seen as one of the world's most notorious terrorist leaders.
TTP was involved in the brutal attack on a school in the Pakistani city of Peshawar Dec 16 in which 150 people, including 140 children, were massacred.
Pakistani authorities had placed a $1 million bounty on Ehsan after he boasted of the Taliban's responsibility for the attempted assassination of teenager Malala Yousafzai, who was shot in the head in October 2012, for wanting to go to school.
Malala has been widely praised for her courage and was awarded the Nobel peace prize last year.
After the attack, Ehsan said: "She was pro-West, she was speaking against (the) Taliban and she was calling President (Barack) Obama her idol. She was young, but she was promoting Western culture in Pashtun areas."
At that time, Ehsan was spokesperson for the TTP, the Pakistan wing of the Taliban, which carried out the attack and other terrorist atrocities.
Last year, Ehsan, along with other former commanders of the TTP, formed the Jamaat-ul-Ahrar.
On his LinkedIn page, Ehsan described Jamaat-ul-Ahrar as his current employer. The group's leader, Omar Khalid Khorasani, is considered to be one of the most ruthless terrorists in the world and has been compared in terms of his barbarity to Abu Bakr al-Baghdadi, the leader of the Islamic State (IS).
The disclosure that Ehsan had an open profile on LinkedIn was potentially embarrassing for the site. Other social networking sites such as Facebook and Twitter have been criticised for failing to clamp down on hardliners who have been using their sites to promote extremism.
Jihadis had boasted of possessing a "dirty bomb" and nuclear material on Twitter, media reported in November last year.
Also, according to a report in December, the IS used Twitter to ask for suggestions on ways to kill the Jordanian pilot whom it had captured.
In October, the Jamaat-ul-Ahrar threatened attacks against Britain in reprisal for the arrest of Anjem Choudary, the radical Islamist cleric and eight other British extremists.
LinkedIn took down Ehsan's account Friday.
A LinkedIn spokesperson said the company's security team had decided to "restrict it (the account)". But she said it was not clear if the account belonged to Ehsan or was a fake account, established by another party. She said the Internet Protocol (IP) address of the account, indicating where in the world it was set up, suggested that it was fake.
The spokesman added: "(I) can't say for certain that it is someone else... But I can say that our security team has a high degree of confidence that it is a fake account, which is reason enough to restrict it. (I) also can't say for certain who might have set it up, if it is fake."