As world leaders offered condolences to New Zealand after a deadly shooting rampage at two mosques was livestreamed on social media, the Canadian government quietly went a step further — suspending its social media advertising for three days.

Public Services and Procurement Canada told CBC News Monday evening that it pulled its ads from social media platforms hours after the attack went live. The ads were reinstated Monday, said department spokesperson Rania Haddad.

"In light of the tragic events in New Zealand, and the subsequent proliferation of content related to these events on various social media channels, PSPC, on the recommendation of its agency of record, temporarily suspended Government of Canada advertising on social media channels," Haddad told CBC News in an email.

It's not clear which social media sites were stripped temporarily of government ads, or what changed to allow the government to reverse its decision Monday.

'Very disturbing': Goodale

Fifty people were killed and dozens injured in the shootings in Christchurch at two mosques — the Al-Noor and Linwood — which were filled with worshippers for Friday prayers at the time.

The gunman livestreamed his attack on Facebook. That footage was shared by others on social media before it was removed by social networks.

Twitter, YouTube and Facebook said last week they were working to remove video footage filmed by a gunman in the New Zealand mosque shooting that was widely available on social media hours after the horrific attack. (The Associated Press)

New Zealand Prime Minister Jacinda Ardern described the attack as "one of New Zealand's darkest days."

Police arrested and charged Brenton Tarrant, 28, from the city of Grafton in New South Wales, Australia. Police also disarmed two improvised explosive devices (IEDs) on a single vehicle.

After the massacre, a 74-page manifesto was discovered on social media under Tarrant's name. In it, the author identifies as a white nationalist seeking revenge for attacks in Europe perpetrated by Muslims.

Last year, Ottawa spent $39.2 million on ads — $7.8 million of it on social media. The bulk of that social media buy — 73 per cent — went to Facebook.

Public Safety Minister Ralph Goodale said Friday it was "very disturbing" to see the murderous rampage play out on social media.

Goodale said his government and Canada's international allies continue to "vigorously" engage with social media firms to ensure their platforms are not "purveyors of hate or extremist violence."

"The companies are generally co-operative," Goodale told reporters. "They do not want their facilities used in that way. But quite frankly, we think that they can and should do more to move more quickly in dealing with these kinds of issues.

"The technology exists. The algorithms exist to identify material of this kind that should not appear on the public platforms, or on the dark web for that matter. It should not appear anywhere."

The minister didn't say at the time his government was pulling its ads from social media sites.

Facebook says it acted 'proactively'

A Facebook spokesperson would not comment on the ads, but insisted the company did everything it could following the attack to "proactively identify content which violates our standards."

"We are adding each video we find to an internal database which enables us to detect and automatically remove copies of the videos when uploaded again," said Mia Garlick of Facebook New Zealand. "We urge people to report all instances to us so our systems can block the video from being shared again."

Labour Minister Patty Hajdu recently told CBC Radio's The House social media networks need to do a better job of policing what people post.

Hadju said she personally has reported hateful Facebook comments that could incite violence, and has gotten messages back claiming that the comments don't violate the social platform's policies.

In the wake of SNC-Lavalin and with a federal budget around the corner, labour minister Patty Hajdu talks about both events with guest host Vassy Kapelos. 10:33

"I am frustrated with the companies," Hadju told The House. "And I feel comfortable saying that, because they have a role to play. And I can't imagine what the technology looks like and what the back end looks like in terms of monitoring billions of comments on all of the posts. But something has to be done.

"I know the concept of free speech comes up. But there is a line, and I think when we are inciting hatred to other groups of people in society, it's not good for anyone. So I think we have to have a much deeper conversation about how we are going to manage this."