A Berlin court has begun hearing an appeal by the German tennis player Alexander Zverev against a fine imposed on him for allegedly assaulting his girlfriend, an accusation which he denies.

As the world No 4 competes at the French Open in Paris, his lawyers are fighting his case in court, after he was fined €450,000 (£384,000, $489,000) in October for allegedly trying to strangle Brenda Patea, his then partner and the mother of his three-year-old daughter, Mayla.

The court heard from the prosecutor how, “after a heated argument” at a Berlin flat in May 2020, Zverev allegedly pushed Patea against a wall and strangled her with both hands. Patea had difficulty swallowing and breathing and had suffered from throat pain for several days afterwards, the court was told.

Zverev’s lead defence lawyer, Alfred Dierlamm, told the court the accusations were “unfounded and contradictory”. He said the court would hear evidence from eyewitnesses and would see chat messages, which would give “an objective view of the events”.

The case was quickly adjourned on Friday after Zverev’s legal team lodged a request for the rest of the trial to be held behind closed doors, in order to protect his privacy and the wellbeing of Mayla. The judges are now considering the request.

The trial, for which 10 non-consecutive days have been scheduled, will resume on Monday when a decision on the request for an in camera hearing is expected to be made.

Patea, a former model, appeared in court dressed in a black suit and seemed calm. She was not required to speak. She is due to give evidence close to the start of the trial, according to the court.

Zverev is not required to appear in court at this stage. The trial opening coincides with the French Open which started on 26 May and will continue until 9 June.

The trial is set to run into the dates of the Wimbledon championships and to conclude just before the start of the Paris Olympics. Zverev, a former Olympic champion, is expected to participate in both events. It is unclear if he will be required to attend the court at any point. Before the trial, the 27-year-old said he would not let himself get distracted by the proceedings, and would “keep a clear head”. He said he was confident he would be found innocent.

“I believe in the German system. I do believe in the truth, as well. I do know what I did, I do know what I didn’t do. That’s – at the end of the day – what’s going to come out, and I have to trust in that,” he said last week.

“I do believe that I’m not going to lose this procedure. There’s absolutely no chance I am. That’s why I can play calmly.”

Zverev had previously faced allegations of domestic abuse against a female fellow tennis player, his former girlfriend Olya Sharypova. But the Association of Tennis Professionals, the organisation responsible for the men’s tour, halted its own investigation into the claims in January 2023, after more than two years, due to insufficient evidence.

Zverev defeated Rafael Nadal in the first round of the French Open on Monday, thereby possibly bringing an end to the Spaniard’s years-long domination of the tournament. On Thursday Zverev beat the Belgian David Goffin, securing him a placed in the third round.

He is seeking his first grand slam title, having just won the Italian Open in Rome, and is considered among the favourites. But his legal problems have thrown a shadow over his sporting achievements and he has been questioned frequently over the allegations rather than about his tennis.

The case continues.