"A serious and evolving situation is occurring in Christchurch with an active shooter," police said in a statement.
"Police are responding with its full capability to manage the situation, but the risk environment remains extremely high."
Local media said there were multiple casualties at one mosque and said another had been evacuated, and there were reports that members of the Bangladesh cricket team were also present at one site.
"Police urge anyone in central Christchurch to stay off the streets and report any suspicious behaviour," he said in a statement.
An eyewitness told Radio New Zealand he heard shots fired and four people were lying on the ground, with "blood everywhere".
"They ran back through Hagley Park back to the Oval," he tweeted.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)