Here is what we know so far about the attacks:
During afternoon prayers on Friday – Islam's holy day – a gunman opened fire inside the Masjid al Noor mosque in central Christchurch, killing 41. Another 7 were slain at a second mosque 5 kilometers away in suburban Linwood, 3 of them outside the building. It is unclear where the remaining victim died.
Witnesses said some victims were shot at close range, with a Palestinian man at one of the mosques saying he saw someone shot in the head.
He described shots fired in quick succession and scenes of panic as people started running out "covered in blood."
Another said he saw his wife lying dead outside as he escaped, with one more saying he witnessed children being shot.
Police imposed a citywide lockdown, sending armed officers to a number of scenes, and two improvised explosive devices were found attached to a vehicle and neutralized.
Three men and a woman were detained. One of the men was later charged with murder, and two others remained in custody, though their role in the attacks was not clear.
Police warned Muslims not to visit mosques "anywhere in New Zealand," a country of nearly 5 million where mass shootings are rare.
Amid heightened tensions, the military carried out controlled explosions on two bags left unattended in central Auckland, although they turned out not to be suspicious.
Christchurch city council offered a helpline for parents looking for kids attending a mass climate change rally nearby.
None of the victims has so far been identified but there were people from around the world in the mosque at the time of the attack.
Among them were 6 Indonesians – 3 of whom were reported safe, the country's foreign minister Retno Marsudi said, adding they were searching for the others.
A Saudi Arabian man, two Malaysians, and an unidentified number of Jordanians are among those wounded.
Turkey's foreign minister said two Turks suffered non-life threatening injuries in the attack.
Young children were among 48 people being treated at Christchurch Hospital.
Some narrowly escaped the carnage, including the Bangladesh cricket team who arrived at the Masjid al Noor mosque minutes after the shooting began.
Manager Khaled Mashud said the team saw "bloodied people coming out of the mosque...we kept our heads down in the bus in case of any firing."
He has not been officially named, but Australian Prime Minister Scott Morrison said he was an Australian citizen, and described him as "an extremist, right-wing, violent terrorist."
He published a racist manifesto on Twitter before the shooting then livestreamed his rampage on Facebook.
Entitled "The Great Replacement," the 74-page manifesto said the gunman – who identified himself as an Australia-born, 28-year-old white male from a low-income, working-class family – had wanted to attack Muslims.
The title of the document has the same name as a conspiracy theory originating in France that believes European populations are being displaced in their homelands by immigrant groups with higher birth rates.
A number of pictures were posted to a social media account of a semi-automatic weapon covered in the names of historical figures, many of whom were involved in the killing of Muslims. – Rappler.com