A fan at the US Open tournament in New York City was ejected from a match between Germany’s Alexander Zverev and Italy’s Jannik Sinner on Monday night after allegedly yelling Adolph Hitler references.

Zverev was serving at 2-2 in the fourth set against Sinner when he went to chair umpire James Keothavong and pointed toward the fan who was sitting behind the umpire.

"He just said the most famous Hitler phrase there is in this world," Zverev told Keothavong. "It’s not acceptable."

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US Open logo

The incident occurred after the fourth set. (JEWEL SAMAD/AFP via Getty Images)

Keothavong turned toward the section and asked the fan to identify himself. Keothavong then asked fans to be respectful to both players. During the changeover, the fan was identified by spectators seated near him and was subsequently removed by security.

"A disparaging remark was directed toward Alexander Zverev," United States Tennis Association spokesman Chris Widmaier said. "The fan was identified and escorted from the stadium."

Zverev said he has had people yell disparaging remarks in the past, but never invoked Hitler.

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Alexander Zverev returns a shot

Alexander Zverev, of Germany, returns a shot to Jannik Sinner, of Italy, during the fourth round of the US Open tennis championships, Monday, Sept. 4, 2023, in New York. (AP Photo/Adam Hunger)

"He started singing the anthem of Hitler that was back in the day. It was ‘Deutschland über alles’ and it was a bit too much," the 12th-seeded player said.

"I think he was getting involved in the match for a long time, though. I don’t mind it, I love when fans are loud, I love when fans are emotional. But I think me being German and not really proud of that history, it’s not really a great thing to do and I think him sitting in one of the front rows, I think a lot of people heard it. So if I just don’t react, I think it’s bad from my side."

Jannik Sinner with a towel on his head

Jannik Sinner, of Italy, covers his face with a towel during the fourth round match against Alexander Zverev, of Germany, in the US Open tennis championships, Monday, Sept. 4, 2023, in New York. (AP Photo/Adam Hunger)

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Zverev won the match in five sets 6-4, 3-6, 6-2, 4-6, 6-3. He will play Carlos Alcaraz in the quarterfinals on Wednesday.

The Associated Press contributed to this report.