Police patrols have been increased around the two mosques targeted in the March 15 attacks.
It comes as a threat overshadows preparations for the first anniversary of the attacks, where 51 people died and 40 were injured after a gunman opened fire at Christchurch's Al Noor and Linwood Mosques.
Police say they're following strong lines of inquiry into the threat against worshippers.
On Sunday night, an individual posted a message in both English and Ukrainian to an online message board, which was accompanied by an image of a person wearing a balaclava outside the Al Noor Mosque.
In a statement on Tuesday, Canterbury District Commander Supt John Price said police will be maintaining a visible presence with the added support of the Eagle helicopter.
"The safety of the community is our top priority, and we all have a responsibility to work together, and to remain vigilant to anything that might be worrying or suspicious.
"We have had regular contact and communication with the mosques since the tragic events of last year, and continue to provide reassurance, advice, visibility, and support."
The Muslim community has also urged its members to be extra vigilant.
Supt Price told Magic Talk's Ryan Bridge on Monday police would "absolutely" be looking to hold someone to account.
"I can say that I've got an investigation team working on this with other agencies and that is progressing well.
"We have leads that I believe are positive and that will enable us to, in time, identify that person.
"I don't want people to be scared at all. I want people to trust that we'll get to the bottom of this."
Police say anyone who hears or sees anything concerning should call 111 immediately.
