Australian media reported the gunman came from a town in New South Wales, of which Sydney is the capital, and state police later said they were increasing patrols around mosques in the state in light of the Christchurch attacks.
The manifesto said he carried out the attack "to show the invaders that our lands will never be their lands, our homeland are our own and that, as long as a white man still lives, they will NEVER conquer our lands and they will never replace our people".
Police did not say how the other two people were connected. He said they had disabled one and were in the process of disabling the second.
People have been recommended by the police to stay inside.
"At this stage, we will not be discussing the offenders' possible motivations or the causes of this incident".
Prime Minister Ardern previously described the attack as "one of New Zealand's darkest days", adding: "What has happened here is an extraordinary and unprecedented act of violence".
Prime Minister Ardern had explained that while many people impacted by the shootings were migrants and refugees, "They have chosen to make New Zealand their home, and it is their home".
In the aftermath, the country's threat level was raised from low to high, police warned Muslims against going to a mosque anywhere in New Zealand, and the national airline canceled several flights in and out of Christchurch, a city of almost 400,000.
Police are warning people on social media about the distressing video which captured 17-minutes of the attack.
Police are urging that the "extremely distressing" video not be shared and have asked for it to be removed. My first thoughts go to the relatives and families of the victims whose emotion and sadness we share.
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That's why when I play I try to enjoy the game as much as I can. An all-Spanish affair for the second quarter-final. I'm really very happy for him".
"For a brief period this morning the Mirror website ran some edited footage filmed by the gunman in Christchurch", he said. Flowers, candles and notes have been placed near the mosques where the shooting took place.
Australian Prime Minister Scott Morrison said one of the men in custody was Australian.
He said Australian authorities were investigating any links between the country and the attack, but declined to provide further details about the alleged shooter.
The 1 NEWS broadcaster added that one man arrested by the police had been apprehended outside one of the local high schools. All Christchurch schools have been shut.
A number of improvised explosive devices found on a vehicle after the shootings were defused by police. "They've been made safe by the defence force", Bush told reporters. Tarrant has been charged with murder.
The massacre by at least one gunman during Friday prayers in the city of Christchurch is the country's worst ever mass shooting and was condemned throughout Asia.
Three others are in custody.
"Just heard the news".
Ardern said 30 people were killed at the Al Noor mosque, the city's main mosque, and another 10 at a mosque in the suburb of Linwood.
At the same time, the Canterbury District Health Board said that at least 48 people, including little children, were being treated at the Christchurch Hospital. Injuries range from critical to minor. He said he and others escaped by breaking through a glass door.
Calderdale leaders have offered their condolences and support in the wake of a shootings at mosques in New Zealand.