CHRISTCHURCH - At least forty-nine people were killed and dozens injured in shootings at two mosques in New Zealand's second-largest city of Christchurch on Friday (March 15) in what Prime Minister Jacinda Ardern said was a well-planned terror attack, forcing the government to place the country on its highest security threat level.

Police said all mosques in the country have been asked to close their doors. Christchurch was also initially placed under lockdown.

Ms Ardern said Friday was "one of New Zealand's darkest days".

"This can only be described as a terrorist attack," Ms Ardern said at here televised press conference on Friday. "From what we know, it does appear to have been well planned."

"Two explosive devices attached to suspect vehicles have now been found and they have been disarmed," she added.

"We have lifted our threat level from low to high. We have tightened our response from our agencies at the border, at the airports. In fact, at every level, we have a heightened response."

She said three people in police custody held extremist views, but had not been on any police watchlist. "While we do not have anything to believe at this stage that there were any other suspects, we are not assuming that at this stage".

Police commissioner Mike Bush says the number of people killed has increased to 49 - the authorities had said earlier put the toll at 40.

A man in his late 20s has been charged with murder and will appear in court tomorrow. Mr Bush declined to identify the man.

One of those arrested may have had nothing to do with the attack, the police chief said. The two other people arrested in possession of firearms are still being investigated. Mr Bush said there have had no other threats since the mosque shootings and the police were not looking at more suspects

Australian Prime Minister Scott Morrison earlier confirmed that one of the four people taken into custody is Australian. Media reports had said that a man who called himself "Brenton Tarrant" - a white, 28-year-old Australia-born man - claimed to be the shooter and livestreamed the shooting for 17 minutes.

"I can confirm that the individual who was taken into custody I have been advised is an Australian-born citizen," Mr Morrison told reporters in Sydney.

"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."

Mr Morrison said he has been in contact with Ms Ardern, and that Australian agencies are working with New Zealand authorities.

Witnesses cited by media reports described scenes of carnage and massacre at Al Noor Mosque in central Christchurch and Linwood Mosque.

Of the confirmed 49 people dead, 41 were killed at Al Noor Mosque and seven killed at Linwood Mosque. Another one died in Christchurch Hospital, where dozens, including children, are being treated. Wounds range from minor to critical, health authorities said.

Witnesses told media that a man dressed in a military-style, camouflage outfit, and carrying an automatic rifle had started randomly shooting people in Al Noor Mosque.

A man, who would not give his name, said he was praying in Al Noor Mosque when he heard the shooting start, reported Stuff news website.

He managed to escape, but saw his wife lying dead on the footpath outside. "My wife is dead," he said, wailing. His head was supported by other Muslim men, who prayed for him.

Another man was cited by Stuff as saying he saw children being shot. Dozens of people were shot by a man wearing military uniform, who emptied at least two magazines. "There were bodies all over me," the man said.

Witness Len Peneha was reported by the Guardian as saying he saw a man dressed in black enter Al Noor Mosque, and then heard dozens of shots, followed by people running from the mosque in terror.

He says he also saw the gunman flee before emergency services arrived. Mr Peneha says he went into the mosque to try and help: "I saw dead people everywhere."

Another man who was in Al Noor Mosque told NZ Herald the building was absolutely full for noon prayers. He believed many have been killed.

ESPN Cricinfo reporter Mohammed Isam said members of the Bangladesh cricket team, who are due to play a Test match in Christchurch on Saturday, escaped from Al Noor Mosque. "They ran back through Hagley Park back to the Oval," he tweeted.

Bangladeshi cricketer Tamim Iqbal Khan has tweeted that the "entire team got saved from active shooters".

Oakford Close resident Robert Weatherhead, who took in people who escaped from the mosque, told NZ Herald they described the gunman as a white man in his 30s or 40s and wearing a uniform, but he had not been able to ascertain what the uniform was.

"[They said] 'he had a lot of magazines strapped to his legs'," Mr Weatherhead said.

Linwood Dental Centre practice manager Janine Richmond said she heard about 20 gunshots come from Linwood Mosque at about 1.45pm. She said armed offenders squad (AOS) members with dogs came in and searched the clinic, which is about 50m from the mosque, shortly after.

"They [AOS] have told us to stay here because it's not safe," she told Stuff.co. "We can't leave and we've been told to stay in a room and stay away from the windows."

Reports of the shooting happened as young protesters gathered in Christchurch and cities around the world to demand action on climate change.

Police had cleared Cathedral Square, where thousands of children were participating in the rally, according to Stuff.co. Fifty to 60 children were kept inside the Christchurch City Council building and the building had been placed on lockdown.

The city council offered a helpline for parents looking for children attending the rally. "Please do not try and come and collect your children until police say it is safe for people to come into the central city," they had said.

Christchurch Hospital, which is about 2km from the mosques, was in lockdown, reported the Guardian. A hospital spokesman said some shooting victims were being treated at the emergency department but he could not provide numbers.

"We don't know the detail at this time," he told the Guardian. "The whole campus, including the building I'm in, is in lockdown, we are not venturing outside - that's staff, patients and visitors."

Muslim Association of Marlborough chairman Zayd Blissett said he found out about the shooting from a text sent by the Federation of Islamic Associations of New Zealand (FIANZ) at 2.04pm, saying "50 shot" during Friday prayers in Christchurch.

"I'm just heartbroken. In fact I'm sitting here crying," he said. "This is New Zealand. This can't happen here."

A man in Al Noor Mosque at the time, who would not give his name, was reported as saying there were "bodies all over me". He said the gunman came in with an automatic gun and emptied at least two magazines.

Another man, Mr Ahmad Al-Mahmoud, 37, described the shooter as white-skinned, blond, quite short and wearing a helmet and a bulletproof vest, reported Stuff. Mr Mahmoud and others broke a window in a door to escape from the mosque.

Prayers started at 1.30pm and the gunman came in about 10 minutes later, when everyone was on their knees praying, he said. The gunman let off dozens, if not hundreds of rounds, he said.

Armed police were trying to clear Deans Avenue and Hagley Park. A large number of police were also reportedly at Christchurch Hospital.

About 20 armed police were also clearing buildings in Linwood, including Eastgate Mall, which will be closed for the rest of the day.

Shocked and horrified

Christchurch mayor Lianne Dalziel said she was "shocked beyond words" by the shootings.

"I would never have expected anything like this to happen in Christchurch, I'd never expect this to happen in New Zealand," she said. "I am getting messages from around the country, and from around the world. I know that everyone is shocked".

Ms Dalziel said she was not in a position to comment on the shootings themselves.

She said all civic buildings including the council headquarters, public library and art gallery were in lockdown. She asked people to heed police advice to keep out of the central city, and to stay safe inside a building if they were already in the central city.

Ms Amy Adams, a member of Parliament from Christchurch, tweeted: "Horrified to hear of Christchurch mosque shootings. There is never a justification for that sort of hatred."

Christchurch, with about 388,000 residents, is the biggest city on New Zealand's South Island, hugging the Pacific Ocean coast.

Muslims account for just over 1 per cent of New Zealand's population, a 2013 census showed.

PM Ardern said that the perpetrator "has no place in New Zealand". She called the victims, some of whom may have been migrants or even refugees to New Zealand, part of the community - "they are us", she said.

She said that those who were in attendance at a mosque should have the right to be exercising their religious freedom, but they were not safe. She says actions like this have "no place in New Zealand".

"We represent diversity and compassion, a home for those who share our values, a refuge for those who need it. And those values will not and cannot be shaken by this attack. We are a proud nation of more than 200 ethnicities and 160 languages."

She issued "the strongest possible condemnation of the ideology of the people who did this".

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

First mass shooting since 1990

There hasn't been a mass shooting in New Zealand since 1990, when a man killed 13 people, including two six-year-olds, after a dispute with his neighbour in the seaside town of Aramoana, the New York Times said.

That shooting led to tightened gun laws, including restrictions on "military style semi-automatic weapons", according to the report.

Gun owners must be licensed, a process that includes a review of criminal activity and mental health, attendance at a safety programme, an explanation of how the gun would be used, a residence visit to ensure secure storage, and testimonials from relatives and friends.

Homicides are rare in New Zealand, and gun deaths even rarer. There were 35 homicides countrywide in 2017.

Since 2007, gun homicides have been in the single digits each year except 2009, when there were 11.

But there are plenty of guns. There were 1.2 million registered firearms in a country of 4.6 million people in 2017, according to the Small Arms Survey, a Swiss non-profit.