Police say 49 people have been killed and dozens injured in shootings at two mosques in the New Zealand city of Christchurch when at least one gunman opened fire on worshippers.
Earlier it was reported that 40 had died but police have given new figures at a news conference.
A man, one of several to be detained, has been charged with murder, police say. One of the massacres was streamed live on social media.
It's the country's worst ever mass shooting and has been condemned internationally.
“This is one of New Zealand’s darkest days,” said Prime Minister Jacinda Ardern. “Clearly what has happened here is an extraordinary and unprecedented act of violence.”
“There is no place in New Zealand for such extreme acts,” she said, describing it as a terrorist attack.
Most of the victims are said to have been killed at the Al Noor mosque, the main mosque in the city on New Zealand's South Island, with several more people killed at a mosque in the suburb of Linwood.
Some 48 people, including children, are being treated at Christchurch hospital, New Zealand health authorities have said. Wounds range from minor to critical, they said.
Reports have suggested that those inside the mosques included refugees and migrants.
Four people – three men and one woman – were taken into custody, police say, but they are not sure if others are involved. The prime minister said they were not on a terror watch-list.
Police say a man in his late twenties has been charged with murder. They have added that they are not looking for further suspects.
Australia's Prime Minister Scott Morrison has confirmed that one of the suspects was Australian-born.
He described the massacre as a "vicious, murderous attack" on people of faith, carried out by "an extremist, right-wing violent terrorist".
New Zealand police say their Australian colleagues had no information on the suspects.
The shooting happened on Friday afternoon, local time, during Friday prayers. The mosques, a few kilometres apart, are close to Christchurch city centre.
Eyewitnesses said a white man dressed in a military-style, camouflage outfit and carrying an automatic rifle had started shooting people at random in the Al Noor mosque. Some have described horrific scenes, with the shooting carrying on for several minutes and people being shot outside as well as inside the mosque.
"I did not see who was shooting but I saw that some people were running out through my room where I was in and also I saw some people had blood on their body and some people were limping. At that moment I realised it was really serious," said one survivor, Mohamed Nazir.
There was a lucky escape for the Bangladesh cricket team. It was arriving for prayers at the Al Noor mosque when the shooting happened, one of the team’s coaches told Reuters, adding that all members were safe. “They are shaken but good,” Mario Villavarayen said.
A test match between New Zealand and Bangladesh due to start on Saturday in Christchurch has been cancelled in the wake of the shootings.
Earlier, police said earlier they were hunting “an active shooter” in the centre of Christchurch city.
“The risk environment remains extremely high,” New Zealand Police Commissioner Bush said, adding that police were responding with full capacity.
A protest over climate change had been taking place earlier in the city, attended by thousands of people including schoolchildren. Schools in the city were put on lockdown but this has since been lifted.
Mosques in New Zealand have been asked to close their doors as a precaution. Police said there was no hard evidence of a threat to mosques elsewhere in the country, but the commissioner added that it was not possible to assume the attack was isolated to Christchurch.
Video film purporting to show the shootings was streamed live online and has been circulating on social media. Police have not confirmed its veracity; the authorities say they are trying to take the film offline are advising people not to share it.
"I'm absolutely aware, I have seen social media footage. It's very disturbing, it shouldn't be in the public domain and we're doing everything we can to remove it," said Police Commissioner Mike Bush.
A spokeswoman for Facebook New Zealand said videos which appeared to show the Christchurch shootings had been taken down.
An online manifesto, published shortly before the video was streamed, was linked to from three social media accounts belonging to Brenton Tarrant.
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 the writer links to his self-acknowledged terrorist attack.
A 2013 census showed that Muslims account for just over one percent of New Zealand’s population.
There has been strong condemnation internationally, including from the leaders of many Muslim-majority countries.
Indonesia's foreign minister condemned the act carried out "especially at a place of worship". Reports have suggested several Indonesians were inside at least one of the mosques.
The leader of the biggest party in Malaysia's coalition government described it as a "black tragedy facing humanity and universal peace". A Malaysian was among those wounded and was being treated in hospital, the country's High Commission said.
Pakistan's foreign ministry condemned the attack on social media. Afghanistan's ambassador to the region said three Afghans had been wounded in the attacks.
A spokesman for Turkey's President Erdogan described it as a "racist and fascist" attack.
British Prime Minister Theresa May tweeted on behalf of the UK her “deepest condolences” after a “sickening act of violence”.
European Council President described it as a "brutal attack" that would never diminish New Zealand's "tolerance and decency".