Elon Musk ignited speculation and chatter online when he made a hand gesture twice during a speech celebrating President Trump on Monday.

Speaking at a celebratory rally at the Capital One Arena in Washington hours after Trump was sworn in as president, Musk thanked the crowd for choosing Trump during “a fork in the road of human civilisation”. Musk, who leads Tesla, SpaceX and the social media platform X, and who backed Trump last year during his presidential campaign, added, “I just want to say thank you for making it happen — thank you.”

The billionaire then grunted and placed his hand to his heart before extending his arm out above his head with his palm facing down. After he turned around, he repeated the motion to those behind him.

On CNN, commentators pointed out Musk’s gesture. Erin Burnett, an anchor, noted how striking the action was. The motion soon drew comparisons online to the salute popularised by Adolf Hitler, and others interpreted it as a Roman salute, which is also known as the “Fascist salute” and was later adopted by the Nazis. The Nazi variation of the gesture is illegal in some European countries, including Germany.

“Did elon musk just hit the roman salute at his inauguration speech?” Hasan Piker, a popular streamer, asked on X.

The Anti-Defamation League, which has tangled with Musk in the past, later said on X that Musk had “made an awkward gesture in a moment of enthusiasm” and that it was “not a Nazi salute”. The organisation added that “all sides should give one another a bit of grace”.

Masha Pearl, the executive director of the Blue Card, a foundation that supports Holocaust survivors, said she was “deeply troubled” by Musk’s action, which she called “a Nazi salute”.