Forty-nine people have been killed and four people are in custody after attackers opened fire during Friday prayers at two mosques in the New Zealand city of Christchurch.

READ MORE: Christchurch shootings: 49 dead after attacks at two New Zealand mosques

Here's what we know so far:
- At least 30 people were killed at the Masjid Al Noor mosque in central Christchurch, at least seven people died inside the suburban Linwood Masjid Mosque, and at least three others died outside the same mosque. In all, a total of 49 people were killed.

- Migrants and refugees appeared to be most affected by the shootings.

- At least 20 others have been seriously injured.

- Four people, three men and one woman, are in custody over the attacks.

- A man in his late twenties has been charged with murder.

- New Zealand Prime Minister Jacinda Ardern said the national security threat level has been lifted from low to high, adding the shootings appeared to have been a well-planned "terrorist attack". She described it as "one of New Zealand's darkest days".

- Police have warned there may be more suspects.

- Australia's Prime Minister Scott Morrison said one of those arrested was an Australian citizen and described the suspected attacker as an "extremist right-wing violent terrorist".

- A number of improvised explosive devices found on vehicles after the shootings have been defused by police.

- Officers first received reports of shots fired in central Christchurch at about 1.40pm local time (12.40am GMT).

- All schools in Christchurch were put on lockdown and mosques told to shut their doors.