An Australian is among those who have been arrested after 49 people were killed and dozens more were injured in terrorist shooting attacks at two Christchurch mosques.

Key points: A man has been charged with murder over shootings in the Al Noor mosque, before a second attack on a mosque in nearby Linwood

A man has been charged with murder over shootings in the Al Noor mosque, before a second attack on a mosque in nearby Linwood An Australian is among those arrested

An Australian is among those arrested The ABC has identified Grafton man Brenton Tarrant in livestreamed footage of the attack

At least one gunman with a semi-automatic weapon massacred worshippers gathered for Friday prayers in two locations: a mosque at Deans Avenue in central Christchurch and another mosque in the nearby suburb of Linwood.

New Zealand police arrested three men and a woman in the aftermath of the attacks, and Australian Prime Minister Scott Morrison confirmed one of those taken into custody was an Australian-born citizen.

New Zealand Police Commissioner Mike Bush said one man in his late 20s had been charged with murder, two other people remained in custody and the other — who was armed at the scene — may not have had anything to do with the attack.

The ABC has identified Grafton man Brenton Tarrant as the man visible in livestreamed footage of the attack.

Police in Christchurch did not name the man who had been charged.

Mr Bush said 41 people died at the Masjid al-Noor mosque on Deans Avenue, seven at the Linwood Avenue mosque, and one more later in hospital. Forty people have been treated for injuries at Christchurch Hospital.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 36 seconds 1 m 36 s Jacinda Ardern confirms 40 fatalities from mosque shootings

New Zealand Prime Minister Jacinda Ardern said the attacks had clearly been "well-planned" and labelled this "one of New Zealand's darkest days".

"It is clear that this can now only be described as a terrorist attack. From what we know, it does appear to have been well-planned," she said.

"These are people who I would describe as having extremist views, that have absolutely no place in New Zealand, and in fact have no place in the world.

"While we do not have any reason to believe at this stage that there are any other suspects, we are not assuming that at this stage."

Ms Ardern went on to offer "the strongest possible condemnation of the ideology of the people who did this".

"You may have chosen us, but we are utterly reject and condemn you."

Mr Morrison said Australia was grieving with New Zealanders over the "extremist, right-wing terrorist attack".

"As family members with our New Zealand cousins today, we grieve, we are shocked, we are appalled, we are outraged, and we stand here and condemn absolutely the attack that occurred today by an extremist, right-wing, violent terrorist," he said.

A vigil was held on Friday night at Australia's largest mosque, where hundreds of people gathered to pray for the victims of the shootings.

Bombs found in car as Christchurch goes into lockdown

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 48 seconds 1 m 48 s NZ Police Commissioner Mike Bush says 49 people have died in the Christchurch terror attack

New Zealand police confirmed in the hours after the shootings they had taken three men and a woman into custody.

Two improvised explosive devices (IEDs) were found on a nearby vehicle, but defence force officers disarmed one and are still working on disarming the second.

"There have been huge acts of bravery to apprehend these people, but let's not assume that the threat is over. We are as visually equipped as we can be," Mr Bush said.

"As you can imagine this is requiring every police and emergency resource that we have available. We have defence force aircraft in Wellington ready to fly more resources into the area, and we will do that from other locations nearby as well.

"This is absolutely tragic. There will be so many people affected."

Map Witnesses reported a shooting at Masjid Al Noor on Deans Avenue in Christchurch. Police also confirmed fatalities at the nearby mosque on Linwood Avenue.

Christchurch Airport said on Facebook that Air New Zealand had cancelled 17 regional flights out of the city, with at least a dozen more arrivals also cancelled, according to the airport's website.

All hospitals in the area have locked their doors, admitting only clear emergencies, while an earlier lockdown on all Christchurch schools has been lifted.

People in central Christchurch have been urged to stay indoors and report any suspicious behaviour immediately to authorities.

For the first time ever, New Zealand's national security threat level has been raised to high.

Ambulances have been rushing injured people to the hospital. ( AP: Mark Baker )

'Distressing' footage of attacks spread online

New Zealand police said they were aware of "extremely distressing footage", recorded and streamed live by an alleged gunman, which was widely spread in the immediate aftermath.

The video shows a gunman entering a mosque and opening fire on dozens of people, before fleeing in a vehicle. He continues to fire his automatic weapon out the window of the car.

"We would strongly urge that the link not be shared," NZ Police said on Twitter.

"We are working to have any footage removed."

Mr Bush also said the video "should not be in the public domain" and confirmed police were trying to remove it.

The ABC has decided not to broadcast any of the video footage, nor take any quotes from alleged manifesto that has also been shared online.

'I saw some people drop dead'

The mosques were reportedly busy at the time of the attacks due to Friday prayers.

Witnesses have described what happened when the first shooter entered the Al Noor mosque.

Bloodied bandages were strewn across the road outside the Al Noor mosque. ( AAP: Martin Hunter )

Farid Ahmed was in his wheelchair when the shooting occurred. He said it was "very peaceful, calm and quiet … then suddenly the shooting started".

"I saw some people had blood on their body and some people were limping," Mr Ahmed said.

"I tried to get out and I pushed myself at the back where my car was, and from there I heard the shooting, it went on six minutes or more.

"I could hear screaming and crying, I saw some people drop dead, some people were running away.

"I was in a wheelchair, so I couldn't get anywhere. He did his massacre inside the mosque."

Ahmad Al-Mahmoud described seeing a man open fire within one of the mosques, before he had to break a window to flee the scene.

"He had a big gun, and lots of bullets. And he came through and he started shooting everyone in the mosque, everywhere," Mr Al-Mahmoud said.

"They had to smash the door, the glass from the window and from the small door. We tried to get everyone to run away from the area because we couldn't open the door for everyone.

"I ran away from the carpark, jumping over the back fence."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 15 seconds 1 m 15 s Ahmad Al-Mahmoud witnessed a gunman opening fire

Another witness who has lived next door to the mosque for about five years said the gunman ran out of the mosque, dropped what appeared to be a semi-automatic weapon in his driveway, and fled.

Len Peneha said he then went into the mosque to try and help the victims.

"I saw dead people everywhere. There were three in the hallway, at the door leading into the mosque, and people inside the mosque," he said.

The Bangladeshi cricket team was also caught up in the attack, fleeing from outside the Al Noor mosque where they were headed for Friday prayers.

"Entire team got saved from active shooters!!! Frightening experience and please keep us in your prayers," batsman Tamim Iqbal tweeted.

ABC/wires