Andy Murray has criticised world number one Novak Djokovic for staging the Adria Tour exhibition tournament without adopting any Covid-19 precautions after the Serbian and three other players tested positive for the coronavirus.

Grigor Dimitrov, Borna Coric and Viktor Troicki also returned positive tests after playing in the Balkan tournament where players were seen hugging at the net, playing basketball, posing for pictures and partying like they did in pre-Covid-19 days.

Murray said he hoped the players and their family members who tested positive recovered soon and added that the tournament should not have gone ahead in hindsight.

"Obviously it's not surprising how many players have tested positive when you see the scenes and the images and the videos from the tournament and the players party with no social distancing in place," Murray said.

"I've seen some people say this puts the U.S. Open in doubt but the measures and the protocols they have in place are completely different to what was going on in Serbia and Croatia.

"For a start, there will be no fans and the players will now know we can all be affected by this, it doesn't matter who you are, we need to respect the rules."

The players, however, did not break any government protocols in Serbia or Croatia with both countries easing lockdown measures weeks before the event.

Murray enjoyed a winning return to action on Tuesday as he beat Liam Broady in the 'Battle of the Brits' charity tournament at the national tennis centre in west London.

The twice Wimbledon champion and former world number one eased to a 6-2 6-2 victory over the British number six in his first competitive match since the Davis Cup Finals in November.

The week-long event, organised by Murray's brother Jamie is being played behind closed doors with strict health protocols in place.

While there were chair umpires, players picked up their own balls and towels and they did not change ends.