World number one Novak Djokovic said Tuesday he had tested positive for coronavirus, the Serb star becoming the fourth player to contract the virus after taking part in his exhibition tennis tournament in the Balkans.

Djokovic, who is "not showing any symptoms" according to a statement from his spokesperson, joins Grigor Dimitrov, Borna Coric and Viktor Troicki in testing positive for COVID-19. 

Djokovic said his wife Jelena also tested positive while the results of their children were negative.

"I am extremely sorry for each individual case of infection," the 33-year-old Serb said in a statement.

"I hope that it will not complicate anyone's health situation and that everyone will be fine," the 17-time Grand Slam winner said, adding that he would go into self-isolation for the next 14 days. 

Bulgaria's Dimitrov, the world number 19, announced on Sunday he had tested positive after pulling out of the event, the biggest since the tennis season was halted because of the pandemic.

Croatia's Coric and Troicki of Serbia also followed suit on Monday, revealing they also had tested positive.

The final in the Croatian coastal town of Zadar was cancelled Sunday while the final stop in Bosnia, due in early July, has also been scrapped after the news of Djokovic's infection. 

"Unfortunately, due to all events in the past days we decided that now the most important thing is that the epidemiological situation is stabilised and everyone recovers," tournament director Djordje Djokovic, the player's younger brother, said in a statement.

"Now we remain focused on the support to all those infected ... wishing that they recover as soon a possible."

Some 4,000 fans had watched the first leg of the tournament in Belgrade earlier this month, while a similar crowd attended the Zadar event.

"What was meant to be a major, nice tennis story ended with an even bigger collapse," Croatia's Sportske Novosti daily newspaper commented on Tuesday.

"Damages could be immense, for both the health of many and (Croatia's) tourism."

Feliks Lukas, director of WTA Croatia Bol Open, earlier warned against "incredibly bad" organisation in Zadar.

Local media reported that social distancing measures were not respected by fans or players in Zadar, as was also the case in Belgrade. 

The slew of positive tests raises questions over the sport's planned return in August.