YouTube, Facebook and Twitter are struggling to stop videos of the Christchurch attack spreading on their platforms, as users upload new copies of the footage faster than the sites can take them down.

Tech companies were swift to ban the gunman’s video of the mosque shootings, but have struggled to enforce this rule due to the difficulties of identifying new copies of the footage, which was initially livestreamed on Facebook.

One version of the video monitored by the Guardian was left live on Facebook for at least six hours, while others were available on YouTube for at least three.

Many traditional media sites including MailOnline, the Mirror and the Sun also hosted edited videos of the same footage, although MailOnline and the Mirror later admitted this was a mistake and removed the videos.

MailOnline also uploaded the alleged attacker’s full 74-page manifesto to its website, deleting the document after being accused of spreading terrorist material. A spokesperson said: “A link was briefly carried to the gunman’s ‘manifesto’. This was an error and swiftly corrected.”

The spokesperson also said: “In common with many other news organisations around the world, MailOnline carried for a time a very short excerpt from beginning of the Christchurch mosque gunman’s video that showed no violence or victims. On further reflection, we decided to remove it some hours ago.”

The gunman’s 17-minute footage of the attack was initially uploaded to Facebook via a mobile app called LIVE4, which is designed to allow extreme sports enthusiasts to stream footage from personal body cameras. Copies of the footage were then downloaded and uploaded to other social media sites.

Downing Street issued a coded criticism of tabloid news outlets, suggesting they should follow the lead of tech companies and remove videos posted by the attacker.

“Facebook, Twitter, YouTube and other providers have taken action to remove the video and other propaganda related to the attack. The government has been clear that all companies need to act more quickly to remove terrorist content. There should be no safe spaces for terrorists to promote and share their extreme views and radicalise others,” a No 10 spokeswoman said.

Britain’s most senior counter-terrorism officer, the Metropolitan police assistant commissioner Neil Basu, warned those circulating the footage made by the attacker of the killings could be subject to criminal prosecution.

“Sharing terrorist propaganda serves only to cause harm and is seized upon by extremists seeking to divide communities. Furthermore dissemination of such material may result in a criminal investigation,” he said.

“Mainstream media companies should also consider very carefully whether it is truly in the public interest to host anything that might inspire hate crime.”

Facebook’s community standards explicitly ban “individuals engaged in mass murder” from having a presence on its network, and the company has deleted the account associated with the suspect. But eight hours after the attack, videos were still live, obscured behind a warning they may “show violent or graphic content” but not deleted.

MailOnline’s version of the story featured an autoplaying clip of 18 seconds of the suspect’s livestream, showing him leaving his car, weapon in hand, cutting it as he enters the front door of Al Noor mosque. There was a version of the clip autoplaying on its homepage.

The Sun took a similar approach. A spokesman for the paper told the Guardian: “We recognise that in the aftermath of horrific events such as these, there will be sensitivities around reporting, and we take those responsibilities seriously.

“We have thought long and hard about how much of the easily available material currently on social media we should host on our site in order to shed light on this barbarous attack and the twisted ‘motive’ behind it. We have not published any video which depicts any act of actual violence, nor have we published or linked to the hate-filled manifesto.”

On the Mirror’s website, a longer clip led the story, showing the same footage of the attacker entering the mosque, cutting over the footage of the attack, and resuming the clip as the gunman walks back out of the building towards his car. That video was removed following inquiries from the Guardian, and the editor-in-chief of the Mirror’s parent company later apologised, saying: “It is not in line with our policy relating to terrorist propaganda videos.”

Tech companies said they were working to keep the videos off their sites, following requests from groups including the US-based Muslim Advocates to remove the footage.

Mia Garlick of Facebook New Zealand said: “Our hearts go out to the victims, their families and the community affected by this horrendous act. New Zealand police alerted us to a video on Facebook shortly after the livestream commenced and we quickly removed both the shooter’s Facebook and Instagram accounts and the video.

“We’re also removing any praise or support for the crime and the shooter or shooters as soon as we’re aware. We will continue working directly with New Zealand police as their response and investigation continues.”

On YouTube, uploaded clips were initially presented as “inappropriate content”, hidden from underage users but available for adults logged in to watch if they actively consented. As the company’s moderation work kicked in, the most graphic videos were removed, but edited versions with the most explicit violence removed remained available on the site.

A recent change to YouTube’s search policy has helped keep the most graphic videos hidden: if the site recognises a particular search term, such as the alleged shooter’s name, as related to news, it explicitly boosts video from news organisations. Videos from sources including the Guardian, CBS News and ABC News were presented ahead of edited re-uploads of the attack itself.

In a statement, a Google spokesperson said: “Our hearts go out to the victims of this terrible tragedy. Shocking, violent and graphic content has no place on our platforms, and is removed as soon as we become aware of it. As with any major tragedy, we will work cooperatively with the authorities.”

Twitter also tried to take down the most egregious re-uploads. “We are deeply saddened to hear of the shootings in Christchurch. Twitter has rigorous processes and a dedicated team in place for managing emergency situations such as this. We will also cooperate with law enforcement to facilitate their investigations as required,” a spokesperson said.

• Crisis support services can be reached 24 hours a day. In New Zealand, the crisis support service Lifeline can be reached on 0800 543 354. In Australia, Lifeline is 13 11 14. In the UK and Irish Republic, contact Samaritans on 116 123. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. Other international helplines can be found at www.befrienders.org.