An app was at the centre of a major transnational sting - including 35 arrests and $3.7 million in assets in New Zealand.

Tech commentator Paul Brislen said the FBI's app, Anom, was installed on black market mobile phones that had been stripped of all their normal functions, like the ability to make phone calls or send text messages.

For law enforcement to get the app into the criminal circles, the app was unwittingly distributed by fugitive Australian drug trafficker Hakan Ayik, after he was given a handset by undercover agents, the ABC reported.

Ayik recommended the app to criminal associates who would purchase the handset pre-loaded with Anom on the black market, the ABC said.

Read more: New Zealand Herald