A million-dollar reward is up for grabs for information about the assassination of a Turkish diplomat and his bodyguard in Sydney almost four decades ago.

The Justice Commandos of the Armenian Genocide, an Armenian militant group active in the mid-70s and '80s, claimed responsibility for the assassination.

Turkish Consul-General Sarik Ariyak, 50, and his bodyguard, Engin Sever, 28, were shot outside a house on Portland Street in the exclusive suburb of Dover Heights at 9.45am on December 17, 1980.

The pair were leaving the house in separate cars when they were shot multiple times at close range by two hitmen who fled the scene on a motorbike.

Ariyak died on the scene and Sever died soon after at St Vincent's Hospital.

Despite extensive police inquiries, no one was ever charged.

Now the NSW Joint Counter Terrorism Team have now established Strike Force Esslemont to re-investigate the murders.

The reward for information that leads to an arrest and conviction jumped from $250,000 to $1million.