The NSW state coroner has found twin blasts that struck the Israeli consulate and a sporting club in Sydney 40 years ago were "acts of international terrorism" perpetrated by the "May 15" organisation. 

The people responsible for the bombings at the consulate in the city's CBD and Bondi's Hakoah Club on December 23, 1982, which left two people injured, have never been found. 

On the 40th anniversary of the bombings, state coroner Teresa O'Sullivan handed down the findings of an inquiry into the explosions, which was launched earlier this month. 

Ms O'Sullivan found Hussayn Al-Umari — the founder of the defunct international organisation known as May 15 — orchestrated the attacks and the group received assistance from "one or more local supporters". 

The findings also revealed that the two bombs used in the attacks were made overseas by Al-Umari. 

"This inquiry is important to both to the victims of the bombings at the Israeli consulate and the Hakoah Club and the community generally," Ms O'Sullivan said in her conclusion. 

"It serves to make an official record of the potentially catastrophic events on December 23, 1982." 

Earlier this month, the inquiry heard Al-Umari was known as the "grandfather of bombmakers".

He is wanted by the United States on several charges, including his alleged role in the August 1982 bombing of Pan Am Flight 830 while it was en route from Japan to Hawaii. 

International experts who gave evidence to the probe suggested the bombs used in the blasts matched at least 20 other explosives either detonated or located around the world. 

NSW Police Assistant Commissioner Mark Walton said the findings were an important step in seeking justice for the victims. 

The explosion at the Israeli consulate on William Street was caused by a gas-powered explosive device which detonated in the stairwell. 

Less than five hours later, a bomb which failed to detonate properly was found in the boot of a car parked at the Hakoah Club, which was packed with athletes preparing for the Maccabiah Games. 

Shortly after the blasts, police said their investigations found the attacks were "acts of international terrorism motived by Palestinian nationalism". 

One man was charged in 1983, but the case was dropped before the trial. 

Earlier this month, the NSW government increased a reward for information that could help solve the case to $1 million. 

NSW Jewish Board of Deputies CEO Darren Bark welcomed the coronial findings. 

"We thank the NSW Coroner's Court, the NSW government and the NSW Police Force for their steadfast and resolute commitment to pursuing justice," he said. 

"Our community remains hopeful that the perpetrators of this heinous attack will be caught."