Novak Djokovic has apologised and admitted he was wrong to organise the Adria Tour events in Serbia and Croatia after becoming one of four players to test positive for coronavirus.
The world number one's positive test was announced yesterday afternoon, with Grigor Dimitrov, Borna Coric and Viktor Troicki also contracting Covid-19.
In a statement, Djokovic said he and his wife Jelena, who also tested positive, are currently asymptomatic and will self-isolate.
"I am so deeply sorry our tournament has caused harm," he said. "Everything the organisers and I did the past month, we did with a pure heart and sincere intentions.
"We believed the tournament met all health protocols and the health of our region seemed in good condition to finally unite people for philanthropic reasons.
"We were wrong and it was too soon. I can't express enough how sorry I am for this and every case of infection."
Djokovic travelled from Zadar, Croatia to his home in Serbia before being tested for the virus.
"If you attended Adria Tour or were around any attendees please get tested and practise social distancing. For those in Belgrade and Zadar, we will be sharing health resources in the immediate future," Djokovic added. "The rest of the tournament has been cancelled."
The event, which took place in front of crowds with little evidence of social-distancing, was criticised by other players.
Nick Kyrgios called the decision to stage the event "boneheaded" while British number one Dan Evans described it as "a poor example to set".
Reacting to the news of Djokovic's positive test, the controversial Australian posted an apparent clip of a party held during the tournament and tweeted: "Don't @ me for anything I've done that has been 'irresponsible' or classified as 'stupidity' - this takes the cake."
Meanwhile, Andy Murray made a winning return in his first match for seven months with victory over Liam Broady in the Battle of the Brits tournament.
The three-time grand-slam champion had not played since a Davis Cup clash in November due to a bruised bone, but clinched a 6-2 6-2 triumph in Roehampton.
He did not show too much rustiness in the Tim Henman Group fixture in the all-British tournament - hosted by his brother Jamie - at the National Tennis Centre.
Murray broke world number 211 Broady in his first game before the Englishman levelled at 2-2.
It was short respite for Broady though, with the two-time Wimbledon winner breaking in the next game and taking the first set 6-2.
Despite this being Murray's first match since victory against Tallon Griekspoor in November, he was able to keep up his energy levels in the second set to close out the win.
He said: "I served pretty well, I thought I served well throughout the match. I didn't hit the ball that well from the back of the court, had a lot of errors and the balance didn't feel great, but it was all right."
Next up for Murray is a match today against Kyle Edmund, which he insists will be a tricky encounter.
"Kyle played well today, he is fit and hitting a big ball so I'll be surprised if I manage to come through that one," the former world number one added.
"I will try to rest up and hopefully improve a little bit tomorrow. If I serve like I did today and hit the ball a little bit cleaner from the back of the court I will give myself some chances."