According to Süddeutsche Zeitung, Struff received permission from his regional sports association in North Rhine-Westphalia last week. 

It is similar to the measures brought in for German footballers, who can now train in groups of five.

Struff said: "I can understand that such exemptions for athletes are viewed critically by the rest of the population in the current situation, but it's also my job and we have strict requirements."

The current world number 34, whose highest singles ranking was 33 last year, had initially stopped playing due to the crisis, but can now train two to three times a week with coach Carsten Arriens while continuing to follow Government policy on social distancing.

To date, there have been more than 2,800 COVID-19 deaths in Germany, but the country has been praised for carrying out more than 1.3 million tests - the second-highest figure in the world.

There have been more than 125,000 confirmed cases.

Struff is not worried about finances, with his career prize money totalling more than $5 million (£4 million/€4.5 million), but has expressed concern for players ranked lower than him. 

"For those in the world rankings of 100 or maybe 150, it will probably be problematic," Struff said.

"These players will first have to do without travelling with their coaches and physiotherapists, a cycle will be set in motion, and many will fall by the wayside."

Struff had a career-best Grand Slam performance last year at the French Open, reaching the fourth round before being knocked out in straight sets by world number one Novak Djokovic.