Billionaire Elon Musk sparked controversy after making a gesture at an event celebrating US President Donald Trump's inauguration, with some calling it a "Nazi" or "fascist" movement.
However, a leading tracker of anti-Semitism said it appeared to represent a moment of enthusiasm instead.
Mr Musk took the Capital One Arena stage in Washington to huge cheers, pumping his arms and shouting, "Yesssss."
"This was no ordinary victory. This was a fork in the road of human civilisation," he said. "This one really mattered. Thank you for making it happen! Thank you," he said.
Biting his bottom lip, he thumped his right hand over his heart, fingers spread wide, then extended his right arm out, emphatically, at an upward angle, palm down and fingers together. Then he turned and made the same hand gesture to the crowd behind him.
"My heart goes out to you. It is thanks to you that the future of civilisation is assured," he said as he finished the gesture.
The gestures were quickly scrutinised online.
"Did Elon Musk Sieg Heil at Trump's inauguration?" asked the Jerusalem Post.
Claire Aubin, a historian who specialises in Nazism within the United States, agreed Musk's gesture was a "sieg heil," or Nazi salute.
"My professional opinion is that you're all right, you should believe your eyes," Ms Aubin posted on X, aligning with those who found the gesture was an overt reference to Nazis.
Ruth Ben-Ghiat, a historian of fascism, also found the gesture "was a Nazi salute - and a very belligerent one too," she said on X.
The Anti-Defamation League, which tracks anti-Semitism, disagreed.
"It seems that Elon Musk made an awkward gesture in a moment of enthusiasm, not a Nazi salute, but again, we appreciate that people are on edge," it posted.
Democratic Representative Alexandria Ocasio-Cortez blasted the ADL's reaction, saying on X: "Just to be clear, you are defending a Heil Hitler salute that was performed and repeated for emphasis and clarity."
Spokespeople for Mr Musk and Mr Trump did not immediately reply to requests for comment.
Soon after his speech, Mr Musk posted a Fox video clip of portions of his speech on his social media network X, that cut away from the podium when he made the first gesture while facing the cameras. "The future is so exciting," he wrote above it.
Some X users came to Mr Musk's defence, claiming that he was expressing "my heart goes out to you" and criticising posts that suggested otherwise.
Mr Musk has backed the far-right Alternative for Germany (AfD), an anti-immigration, anti-Islamic party labeled as right-wing-extremist by German security services, in an upcoming national election.
Earlier this month he hosted a broadcast with the party's leader on his social media platform.
He has also called for Tommy Robinson, a prominent extremist agitator in the UK, to be released from prison, claiming he was incarcerated "for telling the truth".
Accused of helping fuel anti-immigration riots last summer, Robinson was imprisoned in October after he admitted committing contempt of court over a long-running libel case involving a Syrian refugee.
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