Simona Halep: World number one suffers slipped disc

Simona Halep won her first Grand Slam title at this year's French Open

World number one Simona Halep has suffered a slipped disc that puts her participation in this month's WTA Finals in doubt.

The French Open champion, 27, says she does not know how long she will be out but hopes to be back "soon".

The Romanian retired from Sunday's first-round match against Ons Jabeur at the China Open with a back injury.

"I will discuss with doctors in the next few days and will keep you updated," she said on Twittter.

The injury could force Halep to miss the end-of-season WTA Finals in Singapore, which run from 21 to 28 October.