World No 2 Iga Swiatek is receiving additional security at the Miami Open after she was harassed by a spectator during her practice.
The issue comes after British player Emma Raducanu was targeted by a stalker during last month's Dubai Open.
Media reports said that Swiatek was verbally harassed by a spectator, who has a history of online attacks against the player, during practice on Sunday.
"Security is a top priority. We monitor the network to catch these types of issues. Constructive criticism is one thing, and threats, hate speech or even disturbance during training is another - this cannot be condoned," a spokesperson for Swiatek told AFP.
"We reported the matter to the tournament organiser, as well as to the WTA, which reacted immediately and took additional precautions, such as additional security, for which we are very grateful.
"Ensuring the safety of the players is crucial, they are the ones at the centre of the event, and it is our job to protect them," the spokesperson added.
The WTA did not immediately respond to a request for comment.
Raducanu was left distraught after a man later said to be displaying "fixated behaviour" appeared at a courtside seat during her defeat to Karolina Muchova.
The man was escorted away by security, subsequently given a restraining order and banned from attending WTA Tour events.