Australian Nick Kyrgios has hit out at Alexander Zverev after a video appeared to show the German dancing at a crowded club on Sunday despite the world No. 7 pledging last week he would be self-isolating.
The video was posted on Instagram by German designer Philipp Plein and later deleted. There was no indication when the video was taken.
Zverev's team have yet to respond to request for comment.
Zverev, 23, took part in Novak Djokovic's Adria Tour exhibition event in Serbia and Croatia where Djokovic, Grigor Dimitrov, Borna Coric and Viktor Troicki all tested positive for the novel coronavirus last week.
The German said he and his team had tested negative but would self-isolate and undergo regular testing.
"So I wake up and I see more controversial things happening all over the world," Kyrgios said in an Instagram post. "But one thing that stuck out for me was seeing Sascha Zverev again man, again, again. How selfish can you be?"
Kyrgios previously criticised the organisers of the tournament and hit out at governing bodies for their plans to restart professional tennis during the pandemic.
Djokovic's event saw crowds packed into stands for the opening leg in Belgrade, while players hugged and posed for pictures, attended news conferences together and played basketball during the Croatia event.
Zverev was also pictured along with other players dancing at a club in Serbia during the event.
"If you have the audacity to ... put out a tweet that you made your management write on your behalf saying you're going to self-isolate for 14-days and apologising to ... general public for putting their health at risk, at least have the audacity to stay inside for 14 days," Kyrgios said.