Ahead of the five-year anniversary of the killing of Osama bin Laden, CIA chief John Brennan said Sunday that taking out the head of the Islamic State group would have a "great impact."

US special forces killed Al-Qaeda founder bin Laden in Pakistan on May 2, 2011.

As his agency live-tweeted the events as they unfolded five years ago, the CIA director warned that Al-Qaeda remained a threat and that IS was not just an organisation but a phenomenon.

"We have destroyed a large part of Al-Qaeda. It's not completely eliminated. So we have to stay focused on what it can do," Brennan told NBC's "Meet the Press" talk show.

"Now, with the new phenomenon of (IS), this is going to challenge us for years to come," he added.

Asked if removing IS leader Abu Bakr al-Baghdadi from action was as important as the Bin Laden get, Brennan, who does not often do interviews, was direct.

"He is important, and we will destroy ISIL; I have no doubt in my mind. We have to remove the leadership that directs the organisation to carry out these horrific attacks," he said, using an alternate acronym for the IS group.

"If we got Baghdadi, I think it would have a great impact on the organisation. And it will be felt by them," he added.

"But this is a large, not just organisation, it's a phenomenon. We see it not just in Syria in Iraq, we see it in Libya, Nigeria, and other countries. We're going to have remain very focused on destroying all elements of the organization."

Using the hashtag #UBLRaid, the CIA live-tweeted the raid on bin Laden as if it were happening Sunday, tweeting updates that included the famous picture of President Barack Obama and other high-ranking US officials watching matters unfold from the Situation Room.

"3:39 pm EDT - Usama Bin Ladin found on third floor and killed #UBLRaid," read one tweet.