Kvitova stabbing investigation closes

Czech police have finished their investigation into a knife attack on tennis star Petra Kvitova without enough evidence to charge anyone.

Czech police have ended their investigation into a knife attack on twice Wimbledon champion Petra Kvitova last year that forced her off the court for five months.

Kvitova, who lifted the Wimbledon trophy in 2011 and 2014, required four hours of surgery in December after protecting herself from a man wielding a knife who had gained access to her apartment by posing as a utility worker.

Police received a number of clues from the public but could not identify the attacker.

"It was not possible to find facts that would warrant launching prosecution (of any specific person)," police spokeswoman Jitka Dolejsova said in a statement on Thursday.

Kvitova, 27, was ranked 11th in the world at the time of the attack, in which she sustained injuries to tendons in all four fingers and the thumb on her left hand.

She returned to competitive tennis in May, getting knocked out in the second round at the French Open.

The left-hander won the Aegon Classic in Birmingham in June before exiting Wimbledon in the second round.

Kvitova made it to the US Open quarter-finals and is now ranked 29th in the world.