Cirstea downs Jankovic

Jankovic, who had reached the Roland Garros semi-finals for the past two years, stormed through the first three games before being broken in the seventh. She immediately broke back and claimed the set when 19-year-old Cirstea hit long.

The former world number one, who received treatment for a blister on a toe on her left foot while trailing 3-0, never got into the second set as Cirstea made regular charges to the net to send a series of winners past her.

Jankovic served for the match in the 11th game of the third but the tenacious world number 41 broke when the Serb hit long. Cirstea unleashed a sizzling crosscourt backhand to reach her first grand slam quarter-final against Australian 30th seed Samantha Stosur , who swept aside France's Virginie Razzano 6-1 6-2 in just 73 minutes.

World number two Serena Williams quietly eased into the quarter-finals with a 6-1 6-2 demolition of Canadian Aleksandra Wozniak.

Serena, who labelled her previous opponent a 'cheat' following a dispute over a controversial point, was barely bothered by 24th seed Wozniak, racing through the opening set in 23 minutes.

It took her just half an hour to clinch the second, wrapping up victory on her second match point when Wozniak netted a service return.

The 2002 champion will next face Russian seventh seed Svetlana Kuznetsova, who survived her stiffest test yet to beat Pole Agnieszka Radwanska 6-4 1-6 6-1.

The former US Open champion, who had lost only 11 games at these Championships in the lead-up to the fourth round, clinched the first set when Radwanska clipped the Russian's delivery with her outstretched racket but could not return it.

The second set was a different story as the 12th seeded Pole whizzed through it, hitting a beautiful lob that Kuznetsova could only watch sail over her and making the most of the Russian's temporary lapse in concentration.

Kuznetsova, a steely glint in her eyes, reverted in the third set to the lethal forehands that featured so prominently in her previous matches and a shell-shocked Radwanska surrendered with a mis-hit service return after one hour 42 minutes.