Sewell can be seen in the crowd and a photo from the incident appears to show him throwing a punch.
The tussle at the site followed the anti-immigration March for Australia rally in Melbourne.
NSN members attended the rally and Sewell spoke at the event.
Sewell appeared at court on Tuesday in relation to the allegation he intimidated a police officer in 2024.
Earlier on Tuesday, Sewell crashed a press conference with Victorian Premier Jacinta Allan, claiming the state Government was restricting the public’s right to protest.
Allan and other representatives at the press conference quickly left the scene.
Footage shows Sewell shouting questions at Allan while being physically blocked by security.
“Why don’t Australians have the right to protest? Why do you want to ban us from protesting?” Sewell asked.
As security tried to push him back, he said, “Don’t put your f***ing hands on me”.
Allan released a statement after the incident, stating it was “no surprise that Nazis oppose me and my government”.
“I wear that as a badge of honour,” Allan said.
“We know how these goons operate. They whip up fear to divide our society. They will fail.
“This isn’t about me. It’s about the other people in the community who Nazis target – like multicultural people, LGBTIQA+ people, First Peoples, and Jews.
“They’re the Victorians who are on my mind right now, and they’re the Victorians who our anti-hate laws will protect when they come into force later this month,” she said.
“As Premier, I’ll always be out and about in public fighting for you, like I am all day today,” she said.
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