Local media said there were multiple casualties at one mosque and that another had been evacuated.
New Zealand police say they are hunting "an active shooter".
BBC reported that police warned people to avoid the area and all schools and a hospital are in lockdown. "I'm sure all of New Zealand will take a look at their approach".
"There is no place in New Zealand for such acts of extreme and unprecedented violence which it is clear this act was".
Media reports suggest that first shooting incident was reported at Masjid al Noor.
Peneha says he went into the mosque to try and help: "I saw dead people everywhere".
Police Commissioner Mike Bush speaks during a press conference at Royal Society Te Aparangi in Wellington, New Zealand. The street has been evacuated and is being patrolled by armed officers.
She said police were working to get the situation under control. This is significant and I can tell you now this is and will be one of New Zealand's darkest days.
Violent crime is extremely rare in New Zealand, and White said Friday's incident would "greatly affect" the country.
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Bangladesh's tour of New Zealand has been called off following a terrorist attack on two Christchurch mosques, in which at least 40 people have been killed.
Eyewitnesses have reported running for their lives to escape a shooter.
"I heard three quick shots then after about 10 seconds it started again it must have been an automatic no one could pull a trigger that quick", he said. They ran back through Hagley Park back to the Oval. "Some were covered in blood".
"Alhamdulillah Allah save us today while shooting in Christchurch in the mosque", tweeted another player, Mushfiqur Rahim.
New Zealand police are treating it as an active shooter situation.
International Cricket Council chief executive David Richardson said the sport's governing body 'fully supports the decision to cancel the test match'.
"The players just started running when they heard the shots".
Mohan Ibn Ibrahim told CNN he was inside the mosque when the shooting began and that he heard the gunman "continuously shooting for ten to 15 minutes".
Parts of central Christchurch are in lockdown.
People in central Christchurch have been urged to stay indoors and report any suspicious behaviour immediately to 111.
He said he was one of the last people to leave the mosque - and said he was praying that the gunman would run out of bullets. Liton Das and Nayeem Hasan were also back in the hotel and have been contacted, and told to stay back at the hotel.