A death threat against Roger Federer, in the form of an Internet posting, has resulted in the tightening of security around the tennis star in China, according to reports.
Federer is scheduled to play in a Masters Series event in Shanghai, starting Monday.
A tournament official told the Shanghai Youth Daily that the recent threat was being taken seriously and that security around Federer would be upgraded.
A posting late last month on the Chinese website baidu.com by a user with the screen name "Blue Cat" contained a death threat against Federer and a graphic image of an execution, the AFP news agency reported.
Security at tennis tournaments and other sporting events became a more prominent issue after tennis star Monica Seles was stabbed in the back during a match in Germany in 1993.