Stuttgart Open tournament organisers are investigating Nick Kyrgios’s claims that he was racially abused during his semi-final loss to Andy Murray on Saturday. Former world No. 1 Murray looked back to his best on grass as he beat Kyrgios 7-6(5), 6-2 to move into the final of the Stuttgart Open on Saturday after the Australian lost his cool in the second set and said he was racially abused by a fan.

On Sunday, Matteo Berrettini beat Murray 6-4, 5-7, 6-3 to deny the Scot what would have been his first title on grass in six years.

After an entertaining opening set in the semi-final where there was nothing to separate the two players, Murray sealed it in the tie-break after which Kyrgios broke his racket and earned a point penalty as well as a game penalty in the second set.

The Australian, who was constantly complaining to the umpire, then refused to continue playing, sitting in his chair until the supervisor came out and convinced him to finish the match.

A frustrated Kyrgios later said that he had retaliated after hearing a racial slur.

“When is this going to stop? Dealing with racial slurs from the crowd?” he wrote on Instagram.

“I understand that my behaviour isn’t the best all the time — but ‘you little black sheep’, ‘shut up and play’ —little comments like this are not acceptable.

“When I retaliate to the crowd, I get penalised. This is messed up.”

“We stand for creating an inclusive environment for all players, staff members and visitors where discrimination of any kind is not tolerated. This attitude is lived by all people involved and responsible,” the organisers said in a statement on Sunday.

“These fundamental values are as important as values like fairness, tolerance and team spirit to us.

“Thus no discriminating actions by the spectators are accepted.

“We have expressed our regret towards Nick Kyrgios and his team and assured that any kind of discrimination is unacceptable. The incident is currently under investigation.”

After an absorbing opening set, where Kyrgios had even got the crowd going with an underarm serve and front ‘tweeners’, he lost his focus in the second and made numerous errors as Murray quickly wrapped up the match and sealed his spot in the final.