Detective Senior Sergeant Mike Johnson of Canterbury CIB said police had interviewed the males, aged 16 and 19, after executing search warrants in the Christchurch area which obtained "a number of items of interest to the investigation".
Both teenagers were arrested and charged with the murder, and would be appearing in the Christchurch Youth Court today.
"The weapon used in the attack on Mr Ikhtiari which we believe to have a blade of at least 140mm long and 20mm wide is still outstanding," Mr Johnson said.
"Despite the arrest of these two males I still appeal to members of the public who have any information about this crime to contact police."
Earlier yesterday he said police were working to enhance dark and distant images from crime camera footage that appears to show two people leaving the scene where Mr Ikhtiari was stabbed to death in Christchurch early on Saturday morning.
The footage shows Mr Ikhtiari's United Taxi Co cab arriving at the area in Worcester Street, near the Barbadoes Street corner, and it is stopped there for a few minutes before the people are seen leaving.
The images appeared to show two people, Mr Johnson said.
"It is very dark, at a distance, and there are some lighting issues. We are working with it, and we may be able to develop it further to see if we can see more detail," he told a press conference at the Christchurch Central Police Station.
Taxi Federation executive director Tim Reddish said he would speak to the Government about a loan scheme so that taxi drivers could purchase enhanced security gear.
Perpetrators of attacks of drivers were now armed, and knives were quite common, he told Radio New Zealand.
"The whole scene is getting far more dangerous than it was previously."
Taxi companies should insist on their drivers taking proper precautions to keep safe, he said.
There was proven technology, like screens and cameras in cabs, to keep drivers safe. But security gear was quite expensive and most drivers did not have a lot of money.
"I will be talking to the government about perhaps trying to introduce some sort of loan scheme that can enable this equipment to be purchased and paid off over time."
