CHRISTCHURCH, New Zealand — New Zealand's prime minister declared Tuesday she would do everything in her power to deny the accused mosque gunman a platform for elevating his white supremacist views, after the man dismissed his lawyer and opted to represent himself at his trial in the killings of 50 people.

"He obviously had a range of reasons for committing this atrocious terrorist attack. Lifting his profile was one of them. And that's something that we can absolutely deny him," Prime Minister Jacinda Ardern told reporters.

Ardern, who also promised to examine the role social media may have played in the attack, demurred about whether she wanted the trial to occur behind closed doors, saying that was not her decision to make.

A student pays respect at a memorial site for the victims of mosque attacks in Christchurch on Tuesday. William West / AFP - Getty Images

"One thing I can assure you — you won't hear me speak his name," she said.

In a passionate speech to Parliament, she urged the public to follow her lead and to avoid giving the gunman the fame he so obviously craves.

"I implore you: Speak the names of those who were lost, rather than the name of the man who took them," she said. "He may have sought notoriety, but we in New Zealand will give him nothing, not even his name."

The shooter's desire for attention was made clear in a manifesto sent to Ardern's office and others before Friday's massacre and by his livestreamed footage of his attack on the Al Noor mosque.

The video prompted widespread revulsion and condemnation. Facebook said it removed 1.5 million versions of the video during the first 24 hours, but Ardern expressed frustration that the footage remained online, four days later.

"We cannot simply sit back and accept that these platforms just exist and that what is said on them is not the responsibility of the place where they are published," she said. "They are the publisher, not just the postman. There cannot be a case of all profit, no responsibility."

Arden said that she had received "some communication" from Facebook's Chief Operating Officer Sheryl Sandberg on the issue. The prime minister has also spoken with British Prime Minister Theresa May about the importance of a global effort to clamp down on the distribution of such material.

"We have been in contact with Facebook; they have given us updates on their efforts to have it removed, but as I say, it's our view that it cannot — should not — be distributed, available, able to be viewed," she added. "It is horrendous and while they've given us those assurances, ultimately the responsibility does sit with them."

Australian Prime Minister Scott Morrison also urged world leaders to crack down on social media companies that broadcast terrorist attacks. Morrison said he had written to the G-20 chairman, Japanese Prime Minister Shinzo Abe, calling for agreement on "clear consequences" for companies whose platforms are used to facilitate and normalize horrific acts.

Lawyer Richard Peters, who was assigned to represent Brenton Harrison Tarrant at his initial court appearance on Saturday, told the New Zealand Herald that Tarrant dismissed him that day.

A judge ordered Tarrant to return to New Zealand's High Court on April 5 for his next hearing on one count of murder, though he is expected to face additional charges. The 28-year-old Australian is being held in isolation in a Christchurch jail.

"He seemed quite clear and lucid, whereas this may seem like very irrational behavior," Peters told the newspaper. "He didn't appear to me to be facing any challenges or mental impairment, other than holding fairly extreme views."

Ardern has previously said that her Cabinet had agreed in principle to tighten gun restrictions in New Zealand and that those reforms would be announced next week. She also had announced an inquiry into the intelligence and security services' failures to detect the risk from the attacker or his plans. There have been concerns intelligence agencies were overly focused on the Muslim community in detecting and preventing security risks.

New Zealand's international spy agency, the Government Communications Security Bureau, confirmed it had not received any relevant information or intelligence ahead of the shootings.