Members of the armed offenders squad raided properties in St Albans and Linwood shortly before 6pm on Thursday.
Police later confirmed a 27-year-old man had been charged with threatening to kill.
He would appear in the Christchurch District Court on Friday morning.
Further charges against the man were being considered, police said.
The other man was released without charge.
Detective Inspector Michael Ford earlier said police searched the two properties after receiving information from a member of the public regarding “concerning communications on the 4chan site”.
4chan is an anonymous online message board known to be frequented by far-right individuals.
On Sunday night, a person made a series of posts on the site using a similar online name to that used by the Australian terrorist who fatally shot 51 people at two Christchurch mosques on March 15, 2019.
The person said they were “originally English”, but grew up in South Africa before moving to New Zealand in 2009.
They said they planned to “take action” on March 15 by carrying out an attack remotely on the two mosques using car bombs.
The explosions would be livestreamed, the person said.
Others on the message board told them not to do anything “stupid or radical”.
Canterbury district commander Superintendent John Price described the threat, which police received via anonymous tip line Crimestoppers, as “medium level”.
It was “credible enough that we took action straight away”, Price said.
It is understood police visited the Christchurch mosques after learning of the online threats and searched them for bombs. Nothing of interest was found.
Price urged people to be vigilant in the lead up to March 15 and report any concerning behaviour immediately.
“Any messages of hate or people wanting to cause harm in our community will not be tolerated – it’s not the Kiwi way.”
Linwood Masjid Imam Abdul Lateef said it was “sad to hear” there were people trying to scare the community.
He thought people would not be worried though as they would not take the threat seriously.
“We rely on NZ police to protect us, and they are doing the best they can do,” he said.
A neighbour told Stuff she met a man who lived at the property a few days ago. He told her he had only just moved into the area, she said. She was shocked to hear why police were at the house.
This story originally appeared on Stuff NZ and has been republished with permission.