A fan was ejected from the US Open after being accused by Alexander Zverev of using "the most famous Hitler phrase there is in this world".

The 26-year-old heard a remark from a spectator in the crowd during his win over Jannik Sinner.

Zverev was serving in the fourth set when he stopped and approached chair umpire James Keothavong.

"This is unacceptable. This is unbelievable," a furious Zverev told the umpire.

Keothavong immediately turned around and asked the man to identify himself but he did not come forward. The umpire then urged fans to remain fair and show respect to both players.

A few minutes later, security personnel stepped on to the side of the court to identify the man with the help of other spectators and eventually ushered him out of the stadium.

"A disparaging remark was directed towards Zverev," a US Tennis Association spokesperson said in a statement. "The fan was identified and escorted from the stadium."

Zverev went on to beat the Italian sixth seed 6-4 3-6 6-2 4-6 6-3 in a match lasting almost five hours to set up a quarter-final meeting with defending champion Carlos Alcaraz.