The Trump-supporting white supremacist who launched a massacre at a New Zealand mosque revealed that he hoped to spark a 'civil war in the U.S.' in his sick manifesto and described the American president as a 'symbol of renewed white identity'.

The gunman, who identified himself on Twitter as Brenton Tarrant from Grafton, New South Wales, Australia, livestreamed the mass shooting inside the Al Noor Mosque.

Tarrant posted a 74-page manifesto explaining the reasons behind the shooting, which is New Zealand's worst ever terrorist attack, leaving 49 dead and 48 injured.

In the document, Tarrant said that he supported President Donald Trump as a 'symbol of renewed white identity and common purpose' but not as a 'policy maker'.

The 28-year-old terrorist claimed he chose to use a gun over other weapons because it would spark a debate around the second amendment.

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In the document, he said he supported President Donald Trump as a 'symbol of renewed white identity and common purpose' but not as a 'policy maker'

Tarrant, 28, also said that he chose firearms to provoke a debate about the second amendment that he hoped would lead to a 'fracturing of the U.S. along cultural and racial lines'

Tarrant added: 'With enough pressure the left wing within the United States will seek to abolish the second amendment, and the right wing within the U.S. will see this as an attack on their very freedom and liberty.

'This attempted abolishment (sic) of rights by the left will result in a dramatic polarization of the people in the United States and eventually a fracturing of the US along cultural and racial lines.'

He made repeated reference to being European throughout and said that his plan -which he said was two years in the making - was inspired by the Stockholm truck attack in April 2017.

He said he wanted to avenge those killed in that attack which was carried out by Uzbek asylum seeker Rakhmat Akilov.

Tarrant wrote that by using guns to commit the attack, it would fuel the debate over firearms in the US and lead to them being banned.

His other heroes include the right wing commentator Candace Owens.'Each time she spoke I was stunned by her insights and her own views helped push me further and further into the belief of violence over meekness.

His hope was that this in turn would spark a civil war and that 'eventually', it would lead to 'the balkanization of the US'.

Trump tweeted on Friday morning that it was a 'horrible massacre'. He has extended the US's full support to New Zealand as it reels from the atrocity.

President Trump decried the attack as a 'horrible massacre' in a tweet on Friday morning

Owens is yet to make a sympathetic remark about the atrocity and responded 'LOL!' with a crying face emoji when Twitter users pointed out she had been mentioned in his manifesto.

The manifesto also included photographs of white children and poems.

Tarrant launched the attack at Al Noor Mosque in Christchurch on the country's South Island at about 1.30pm as Friday prayers were underway.

At about the same time, what appears to be a second shooter opened fire at at mosque in Linwood, which is within 10km of the first attack.

Early reports indicated a shooting at Christchurch Hospital. However, New Zealand Prime Minister Jacinda Ardern said the mosques were the lone targets.

She did confirm multiple bombs were attached to two cars belonging to the suspects near the mosque.

The explosives were disarmed before they could detonate.