Football Australia (FA) has launched an investigation into the behaviour of Sydney United 58 fans who chanted songs with fascist links and displayed apparent Nazi salutes during the Australia Cup final.
The organisation also condemned the booing of the "Welcome To Country" at CommBank Stadium, while the NSW Board of Jewish Deputies described supporters' conduct as "reprehensible."
NPL NSW side United became the first non A-League Men team to reach the tournament's final but their achievement was overshadowed by the behaviour of a section of their supporters as they suffered a 2-0 loss to Macarthur FC.
Some followers of United, formerly known as Sydney Croatia, sang "Za Dom Spremni (For Homeland -- Ready)" -- a chant used by the far-right Ustase movement in Croatia in the 1930s and 1940s.
Images and videos circulated on social media also appeared to show fans carrying out fascist-style salutes.
"Football Australia is today assessing all footage and images available of certain individuals which are of concern to our organisation and the broader Australian football community, including the displaying of the Hitler salute," FA said in a statement.
"Football Australia is working closely with the management of CommBank Stadium and NSW Police to determine strong and swift action on any identified anti-social behaviour, which may also be deemed as illegal in the state of NSW."
FA said eight fans were ejected from the venue.
AAP has contacted Sydney United 58 for comment.
There were also some questionable banners unveiled by United fans at CommBank Stadium, one of which bore a striking resemblance to the flag of Nazi Germany.
Largely red, it contained a white circle in the middle, with "EP" -- an initialism of the club's Edensor Park home -- written in the circle in black typeface.
"These vile symbols and salutes have no place in modern Australian society," NSW Jewish Board of Deputies chief executive Darren Bark said.
"They represent the ultimate manifestation of evil -- an evil which led to the murder of millions of innocent civilians during WWII, including six million Jews and thousands of Australian Diggers who lost their lives fighting against the Nazis during WWII.
"Reprehensible conduct such as this causes immense distress to the victims of Nazi crimes and their descendants, whilst undermining our cohesive multicultural society."
A section of United fans chanted and booed during the Welcome To Country performed by Erin Wilkins, as well as the national anthem.
Former United player and Australia international Craig Foster tweeted his condemnation, apologising to Indigenous Australians and describing the behaviour as a "horrific display of racist hate."
FA chief executive James Johnson telephoned Wilkins during the final to apologise on behalf of his organisation.
"We regret that this occurred and are reviewing all available footage and audio to further analyse the incident," FA said.