At least 50 people were killed and dozens were injured in shootings at two mosques in Christchurch, New Zealand on Friday, authorities said.

Here is what we know about the shooting, which Prime Minister Jacinda Ardern called a "terrorist attack".

What we know about the circumstances of the attack

Video footage widely circulated on social media, apparently taken by a gunman and posted online live as the attack unfolded, showed him driving to one mosque as music played in his vehicle. After parking, he took two guns and walked a short distance to the entrance of the mosque.

The gunman then opened fire. Over the course of five minutes, he repeatedly shoots worshippers, leaving well over a dozen bodies in one room alone.

He returned to the car during that period to change guns and went back to the mosque to shoot anyone showing signs of life.

Two of the injured, including a four-year-old child, are in a critical condition, Bush said.

Radio New Zealand quoted a witness inside the mosque saying he heard shots fired and at least four people were lying on the ground and "there was blood everywhere".

What we know about the suspects

A 28-year-old Australian suspect, identified as Brenton Harrison Tarrant, appeared in Christchurch district court on Saturday at 11:00 am local time.

Tarrant has been charged with murder and was remanded without plea. He will return to court on April 5.

New Zealand Police wrote on Twitter: "While the man is currently facing only one charge, further charges will be laid." Two others are currently in custody.

The charged suspect held extremist views but had not been on any police watchlists, the Prime Minister said.

Australian Prime Minister Scott Morrison said that an Australian citizen with far-right extremist views was among those taken into custody.

An Australian man is believed to have published an online manifesto, shortly before the video was streamed. The document was linked to three social media accounts belonging to Brenton Tarrant, according to Storyful.

The writer of the manifesto says he is 28 and Australian. The document, stretching to more than 16,000 words, rails against immigration and cites a list of events from various periods of history which inspired his self-acknowledged terrorist attack.

He also says that he decided to commit the murders following a trip to Europe in 2017 when he saw Emmanuel Macron triumph over his far-right opponent Marine Le Pen in the French presidential election and saw people he believed were immigrants living in France.

He denied that he was acting on behalf of any groups.

Police searched a property in the southern city of Dunedin in connexion with the shootings investigation. Evacuations of properties in the immediate area have taken place as a precaution.

The two other people initially detained with the attacker have been released, according to Bush.

No further threats were reported since responding to this incident, police said.

Shooting at mosques in Christchurch, New Zealand 1 2 REUTERS/SNPA/Martin Hunter 1 2 1 2 1 2 REUTERS/SNPA/Martin Hunter 1 2 REUTERS/SNPA/Martin Hunter 1 2 REUTERS/SNPA/Martin Hunter 1 2 1 2 1 2 REUTERS/SNPA/Martin Hunter

What we know about the victims

New Zealand's prime minister said many of those caught up in the shootings may have been migrants and refugees.

Hospitals said children were among the victims.

The Indonesian foreign minister was cited by media as saying six Indonesians had been inside the mosque when the attack occurred, with three managing to escape and three unaccounted for.

The consul of Bangladesh in Auckland said three Bangladesh citizens were killed and four injured.

Afghanistan's ambassador to Australia, New Zealand and Fiji, Wahidullah Waissi, said on Twitter three Afghans had been wounded.

Two Malaysians were also wounded in the attack, its foreign ministry said.

Bangladeshi Foreign Minister Shahriar Alam said it was "extremely lucky" the country's cricket team did not suffer casualties. The team, in the city to play a match against the New Zealand national team, arrived for Friday prayers as the shooting occurred.

"I can't even imagine what would have happened if they were there five minutes earlier," he said on social media.

Reactions in New Zealand and abroad

"They are us," Prime Minister Jacinda Ardern said of the victims.

"The person who has perpetuated this violence against us is not. They have no place in New Zealand," she said as she condemned the attack.

The country has been placed on the highest level of security alert. All mosques in New Zealand had been asked to shut their doors, police said.

"I condemn the violent, extremist, right-wing terrorist attack that has stolen the lives of so many innocent New Zealanders as they went about their peaceful practice of worship at their mosques in Christchurch today," the Australian Prime Minister tweeted.

British counter-terrorism officials said they were ready to help their counterparts in New Zealand to investigate the shootings. Meanwhile, the UK and France are stepping up security near religious sites following the attack.

The United States presidency called the deadly attack at two New Zealand mosques during Friday prayers a "vicious act of hate."

"All our thoughts go to the victims of the heinous crimes committed against the mosques of Christchurch in New Zealand and for their loved ones," tweeted French President Emmanuel Macron.

Political and Islamic leaders across Asia and the Middle East expressed their disgust at the deadly shooting.

"Indonesia strongly condemns this shooting act, especially at a place of worship while a Friday prayer was ongoing," Foreign Minister Retno Marsudi said in a statement.

Turkish President Tayyip Erdogan's spokesman condemned what he called a "racist and fascist" attack.

"This attack shows the point which hostility to Islam and enmity to Muslims has reached," Ibrahim Kalin wrote on Twitter.

Pakistan's foreign ministry spokesman Mohammad Faisal condemned the incident on social media, using the hashtag #pakistanagainstterror.

Ordinary people expressed their horror online about the widely circulated video of the shooting.

"Feeling very sick, that person is brainless and a savage," said one Indonesian twitter user who identified himself as Farhan Adhitama.