There will be no fans at this year's Serbia Open, says event organiser Djordie Djokovic, brother of world number one Novak Djokovic.
The Serbia Open hasn't been held as a 250 event on the ATP tour since 2013 but Belgrade has stepped up with Hungary unable to host their 250 tournament.
It will be held as a men's and women's joint event.
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This year, like many others, the tournament will be held behind closed doors.
"Unfortunately, there will be no fans this year as we're in a difficult situation with a lot of people contracting the virus on a daily basis," the ATP 250 event's organiser Djordje Djokovic told Serbia's Nova S television.
"It's a very difficult year for everyone and the restrictions have resulted in a lot injuries. Regrettably, Borna Coric and Stan Wawrinka have had to pull out but it's still going to be a very strong field.
"Apart from Novak, Dominic Thiem, Gael Monfis and Aslan Karatsev will enter the tournament, as will Serbia's Filip Krajinovic, Laslo Djere and Miomir Kecmanovic. A lot of top 30 players will be here."
The tournament stats on April 19 and runs through to the 25th.
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