A police officer responds following shooting at Linwood in Christchurch, New Zealand. Picture: Reuters

Christchurch - At least one gunman killed 49 people during Friday prayers at two New Zealand mosques in the country's worst ever mass shooting.

WHAT WE KNOW

* Forty-nine people were killed and 20 seriously injured in the shootings, which the Prime Minister has described as a "terrorist attack".

* New Zealand police have arrested three people in connection with the attacks including one man who has been charged with murder.

* One man will appear at a Christchurch court on Saturday.

* A gunman livestreamed the shootings on Facebook, after publishing a "manifesto" in which he denounced immigrants, calling them "invaders".

* The country's national security threat level alert was lifted from low' to 'high'.

* Police found two explosive devices attached to the suspects' vehicles, which have since been disarmed.

* Almost 50 people were treated at Christchurch Hospital for gunshot wounds, including young children.

* A police presence has been placed at mosques around the country and ramped up throughout Christchurch.

* The Bangladesh cricket team narrowly avoided being caught up in the shooting while on a bus approaching one of the mosques while in the city for a match, which has since been cancelled.

* Three Bangladeshis were among the dead and one was missing, the consulate said.

WHAT WE DON'T KNOW

* The identities of the victims - further nationalities could be among the casualties, with Afghan and Malaysian government confirming nationals injured in the attack.

* Whether there are more suspects - Prime Minister Jacinda Ardern has said the government has no reason to believe there are more suspects, but was not assuming that was the case and intelligence services and police were working on establishing this.

* The confirmed identity of the suspects.

* The suspects' ideology and preparation for the attack - Prime Minister Ardern described them as having "extremist views", but New Zealand's police commissioner said the man charged with murder was not known to intelligence services.

Reuters