After meeting with the Australian Federal Police and domestic intelligence agency Asio, state police said additional information led them to conclude the incident should be treated as a terrorist attack.
Commissioner Shane Patten said police had no information prior to the fire suggesting an arson attack was imminent.
He declined to give further details as the investigation continues.
Patten’s declaration comes a day after Prime Minister Anthony Albanese described the incident as “quite clearly terrorism” while acknowledging police had not yet made a decision. He called his explanation a “personal opinion.”
On Monday, Premier Jacinta Allan said the terrorism designation would give police additional resources for the investigation.
Jewish community leaders said they believed the attack was an extension of a recently recorded rise in anti-Semitism in Australia and heightened fears of violence.
Several believers were inside the building at the time of the fire, and they testified that they heard banging and a window breaking, followed by liquid pouring into the building and catching fire.
“It all happened pretty quickly,” synagogue board member Benjamin Klein, who interviewed witnesses, told The Age newspaper.
After officers at the scene were confronted by angry and scared worshipers on Friday, Mr Patton said police were focused on ensuring their safety.
“We have…deployed additional police officers in areas where large numbers of Jews live and gather,” he said.
Allan also urged the city to support its Jewish community.
“We cannot allow conflicts abroad to continue to serve as a cover for (this) action.”
