Petra Kvitova was on Tuesday undergoing surgery after suffering a "severe" hand injury when she was attacked by an intruder with a knife in her apartment.

The two-time Wimbledon champion said she felt shaken, but fortunate to be alive after the incident at her property in Prostejov.

Kvitova suffered damage to the ligaments and tendons in her left hand and the world number 11 is set to discover the extent of her injuries after an operation.

The 26-year-old Czech posted on Twitter and Facebook: "Thank you for all your heartwarming messages. As you may have already heard, today [Tuesday] I was attacked in my apartment by an individual with a knife.

"In my attempt to defend myself, I was badly injured on my left hand. I am shaken, but fortunate to be alive.

"The injury is severe and I will need to see specialists, but if you know anything about me I am strong and I will fight this.

"Thank you all again for your love and support and now I would appreciate some privacy while I focus on my recovery."

It had earlier been announced that Kvitova would not compete in the Hopman Cup next month due to a foot injury. 

She suffered a stress fracture in her right foot and a slower-than expected recovery led her to withdraw from the team event that starts on January 1.