An indecent assault brought traffic to a standstill around the Australian Open last night, with tennis fans warned to avoid the area due to safety concerns.

About 9.30pm Wednesday police closed Olympic Boulevard at Melbourne Park, it was reopened one hour later.

Tennis spectators at Hisense Arena and Rod Laver Arena were told the boulevard was closed "due to a safety issue".

A police spokesman said a woman was "indecently assaulted" by a man, about 6.45pm.