Australian Open organizers have issued a reminder to players and their entourages about their policy on "inappropriate flags" after a video emerged showing Novak Djokovic's father posing for pictures with fans holding Russian flags.

Four people were kicked out of the Australian Open after displaying Russian flags — which have been banned from Melbourne Park — and threatening security guards, police and Tennis Australia said Thursday.

A Victoria Police spokeswoman said the four have not been charged but were evicted from the site.

The flags, at least one of which included an image of Vladimir Putin, were being waved during a gathering outside of Rod Laver Arena after Novak Djokovic beat Russian player Andrey Rublev in straight sets in the quarterfinals of the year's first Grand Slam tennis tournament Wednesday night.

A video posted on social media showed one supporter on the steps of Rod Laver Arena holding up a Russian flag with the image of Putin on it.

Late on Wednesday another video showed Djokovic's father Srdjan posing for pictures with fans holding Russian flags.

"Players and their teams have been briefed and reminded of the event policy regarding flags and symbols and to avoid any situation that has the potential to disrupt," Tennis Australia said in a statement on Thursday.

"We continue to work closely with event security and law enforcement agencies."

Russian and Belarusian flags were banned from Melbourne Park during the tournament after a complaint from the Ukraine ambassador to the country.

Belarus is a key staging ground for Russia's war in Ukraine, which Moscow terms a "special operation."

Photos on social media also showed one fan in the crowd during Wednesday's match with a "Z" on his shirt.

Russian forces have used the letter "Z" as an identifying symbol on their vehicles in Ukraine following the invasion. Some supporters of the invasion have also used the sign.

Russian and Belarusian players have been allowed to play at the Australian Open, French Open and U.S. Open, but as "neutral" athletes, so their nationalities are not acknowledged on any official schedules or results for the event and their countries' flags are not displayed on TV graphics.

At the Australian Open, two women who represent Belarus — Victoria Azarenka and Aryna Sabalenka — and one man who represents Russia — Karen Khachanov — reached the singles semifinals.