An emotional Waleed Aly has spoken about the horrific terrorist attacks in Christchurch targeting mosques, which have killed at least 49 people.

A video of the powerful address, in which he spoke of the need to come together and criticised those who have previously "demonised particular groups", has gone viral.

The Project co-host began by admitting he had resisted having to make the remarks all day, until he felt "an overwhelming sense of responsibility to do so".

"These won't be my best words," the prominent Muslim academic, journalist, commentator and broadcaster began.

"Of all the things, I could say, that I'm gutted and I'm scared and I feel overcome with utter hopelessness, the most dishonest thing would be to say that I'm shocked.

"There is nothing about Christchurch that shocks me."

Aly said he wasn't shocked when six people were shot to death at a Quebec mosque two years ago, or when a man drove a van into a London mosque six months later.

"And I wasn't shocked when 11 Jews were shot dead in a Pittsburg synagogue late last year, or when nine Christians were killed at a church in Charleston."

The attacks in Christchurch — in which an Australian man opened fire on two mosques, which he livestreamed on social media — "has been coming", Aly said.

On Friday, Aly said he went to a Melbourne mosque, as he does every Friday, and knew what those in Christchurch would have felt in the moments prior, news.com.au reported.

"I know how quiet, how still, how introspective those people would've been before they were suddenly gunned down," he said.

"How separated from the world they would've been feeling until the world came in and tore their lives apart."

Aly said the gunman, who Prime Minister Scott Morrison described as a "extremist right-wring terrorist", had deliberately picked that moment, knowing his victims would be helpless.

"This was slaughter by appointment," Aly said.

"That's what made it scary, because he and other Muslims would not stop going to mosques to worship.

"It feels like fish in a barrel," he said.

Aly spoke about reading the gunman's manifesto, which was shared online before his attacks. He then appeared to read excerpts from it, attacking Islam as a religion of violence and saying that those who are Muslim should expect violence against them.

"How do those words sound when I tell you they weren't part of the manifesto? They were published [on Friday], after the attacks, on an Australian parliament letterhead," he said.

The remarks were those of Senator Fraser Anning, released in the wake of the attack, which have been roundly condemned.

Senator Anning has refused to apologise and even doubled down on the sentiments, which essentially blamed Muslim people for the attacks.

"While I appreciate the words our leaders have said, and in particular Scott Morrison's comments and preparedness to call this terrorism … I have something to ask," Aly continued.

"Don't change your tune now because the terrorism seems to be coming from a white supremacist. If you've been talking about being tough on terrorism for years, and [on] the communities who allegedly support it, show us how tough you are now.

"Now, now we come together. Now we understand this is not a game. Terrorism doesn't choose its victims selectively. We are one community.

"Everything we say to try to tear people apart, demonise particular groups, set them against each other. that all has consequences, even if we're not the ones with our fingers on the trigger."