The ATP is investigating domestic abuse allegations made by world No. 4 Alexander Zverev's ex-girlfriend, the governing body for men's professional tennis announced.

The ATP said in a statement it "fully condemns any form of violence or abuse and will investigate such allegations related to conduct at an ATP member tournament."

In an interview with Slate in August, the German's ex-girlfriend, Olya Sharypova accused him of physically and emotionally abusing her at the ATP Masters 1000 event in Shanghai in 2019.

Zverev was asked about the allegations at a press conference prior to the 2021 US Open in August and he denied the allegations.

"I've always said that the allegations and everything that has been said is untrue," he said.

The 24-year-old also wrote on Twitter in August that no abuse occurred. "I have engaged my German and American lawyers in the matter. They have already obtained a preliminary injunction against the source and the author who published the false allegations. The court followed our arguments and states, the accusations aroused are defamatory and false. The lawyers have therefore initiated further proceedings against the source and the author.

"I categorically and equivocally deny abused Olya. I also fully support the creation of an ATP domestic violence policy."

Zverev also told CNN in a statement that he had "been asking the ATP to initiate an independent investigation for months."

"As stated before, I categorically and unequivocally deny any of these allegations."

Regarding the ATP's investigation, the organization's CEO Massimo Calvelli said in a statement: "The allegations raised against Alexander Zverev are serious and we have a responsibility to address them. We hope our investigation will allow us to establish the facts and determine appropriate follow-up action. 

"We understand Zverev welcomes our investigation and acknowledge that he has denied all allegations. We will also be monitoring any further legal developments following the preliminary injunction obtained by Zverev in the German Courts."

Sharypova also claimed that Zverev tried to suffocate her with a pillow in a hotel room in New York before she fled barefoot in fear of her life.

Screenshots of WhatsApp messages shown to CNN Sport appear to suggest the alleged incident happened on August 23, 2019, a month and a half before the Shanghai Masters event. Last October, Zverev said the allegations are "simply not true."

Sharypova told Slate that her decision to speak out was not about Zverev. "I wanted to be public, to be honest with all of you," she said. "Many girls in this situation are silent. They don't speak about it because they're afraid of comments that it's not true and stuff like that. I just wanted to show that it's not hard to speak about it. 

"It already happened in real life, you already lived it. You know that you said the truth, you know that you're not a bad person, and you didn't deserve this."