It is believed two gunmen opened fire at two central Christchurch mosques, Al Noor and Linwood. 

Australian Prime Minister Scott Morrison confirmed one of the people taken into custody was an Australian-born citizen. 

Shelby Darlow moved from Hay to Christchurch five years ago and said today's event had rocked the city. 

"At the moment it's all a bit of a shock and surreal that something like this could happen in Christchurch," she said. 

"I was at work when everything happened and colleagues had seen articles and because I work in a government building, we went into lockdown. 

"We were located only one kilometre from the mosque." 

Along with her partner and daughter, Ms Darlow is staying at her family's residence as her home is located just three streets from Linwood mosque.

Ms Darlow said it was "very scary" as her daughter was in daycare, but she was unable to see her. 

"We had no idea what was going on and we just had to keep reading the news," she said. 

"We were able to contact the daycare and they provided updates through text message and on the daycare app every hour, which was really good. 

"But in times like this all I wanted was to get my daughter and go home." 

Ms Darlow said she was first notified that her workplace building was in lockdown at 2.20pm (New Zealand time) and was able to pick up her daughter from daycare four hours later. 

"It was just a waiting game and it's just terrible," she said. 

"It'll be a very on-edge night, but hopefully when we wake up tomorrow we can return to some sort of normality.

"It's a very sad day for New Zealand." 

The mother said she has witnessed Christchurch's earthquakes and this was a similar feel. 

"I wouldn't say we're feeling unsafe, but more on-edge," she said. 

"Shops are closed and the city is dead. 

"My partner drove past the mosque just 20 minutes before it happened and he had a friend who was at the mosque but managed to get out safely." 

NSW Police issued a statement assuring the public there is "no ongoing or specific threat to any mosque of place of worship in Sydney or across NSW". 

However, the statement said police have increased patrols and senior officers have reached out to community and religious leaders to offer support and reassurance. 

New Zealand PM Jacinta Ardern called for support and compassion as Muslims were told to avoid mosques. 

"I would hope the outpouring of compassion and support that I know New Zealanders will want to show, show it to them. Show it to the members of the community who sought to worship safely."

Ms Ardern said NZ can still call itself a peaceful nation.

"This is not who we are. This act was not a reflection of who we are as a nation. That is why so many New Zealanders, every New Zealander, I imagine, will be shocked by this today. Because this is not who we are. This is something that all of us will utterly reject and of course it will take time to heal, and tonight our thoughts and prayers need to be with those affected."