Ivanovic hammers Cetkovska

Second seed Ivanovic played with the urgency of a woman late for a lunch appointment as she ruthlessly dismantled Czech Petra Cetkovska 6-0 6-0 in 54 minutes on Court Philippe Chatrier.

While Ivanovic's win was painfully easy, Jankovic's was just downright painful.

Jankovic needed a 10-minute medical time-out after game three of the second set against Poland's Agnieszka Radwanska before she crawled past the finishing line with a 6-3 7-6 victory.

"The whole arm is a mess," said Jankovic, who resembled a wrestler pinned to the floor as the tournament trainer massaged her arm and shoulder back to life.

"I started to feel the pain in the beginning of the second set and since then it's been pain, pain, pain," said the 23-year-old, who will next face Spain's Carla Suarez Navarro.

The Paris crowd had barely got through the scrum at the turnstiles as Ivanovic, who by each passing minute looks like improving on her runner-up finish of last year, showed no mercy against the lamentable Cetkovska.

The unseeded Czech, who had not dropped a set in the tournament, looked like a decent threat going on a high-quality opening rally, but once Ivanovic got her eye in she folded quicker than a bad poker hand.

Ivanovic pounded her with winners and even when the Czech carved out two break points in game five of the second, she slouched with a knowing smile when Ivanovic snuffed out any whiff of a comeback.

"It was much tougher than it probably looked, or the results indicates," said a generous Ivanovic, who has lost a paltry 15 games at Roland Garros so far this year.

"I had to work really hard, and I played almost without mistake today."

Swiss 10th seed Patty Schnyder ended Katarina Srebotnik's unexpected run to the fourth round with a 6-2 6-4 win.

The Slovenian had knocked out Serena Williams, the only former champion in the women's draw, in the third round but was unable to reproduce the heroics on Sunday and went down tamely.

The win put Schnyder through to the quarter-finals here for only the second time, a decade after her last appearance in the last eight.

Schnyder is likely to face much stiffer opposition in the next round as she will face last year's runner-up Ivanovic.

Meanwhile, Spaniard Carla Suarez Navarro beat Italian 26th seed Flavia Pennetta in straight sets 6-3 6-2.