UPDATE 5.30am

Former world number one Ana Ivanovic has retired from professional tennis, aged 29.

The Serb, who won the French Open in 2008, had been struggling with injury problems in 2016, winning only 15 matches. She also did not play on the WTA Tour after the US Open in August.

On her Facebook page on Wednesday, Ivanovic posted: “I have some big news I want to share with you. I have not announced it anywhere else because I think you deserve to hear it first. So what is it? Well, there is no other way to say it – I have decided to retire from professional tennis.”

Ivanovic won 15 career titles, including one grand slam — her 2008 French Open — making her the first and only female grand slam singles winner from Serbia, and the second overall after Novak Djokovic.

In that same year, she was also runner-up the Australian Open, losing 7-5 6-3 to Maria Sharapova in the final, and runner-up in the 2007 French Open.

She was also the first Serbian woman to reach world number one, spending a total of 12 weeks in the top spot in 2008.

EARLIER

Only weeks ahead of the Australian Open, former women’s tennis world No.1 Ivanovic fuelled retirement rumours after posting a cryptic social media message.

The 29-year-old wrote on Twitter that she would share some important news in Britain on Wednesday night (early Thursday AEDT).

“My dear fans & supporters. Pls tune in to my Facebook page tomorrow at 6pm UK time, where I’ll be sharing something important with you live,” she posted.

My dear fans & supporters. Pls tune in to my Facebook page tomorrow at 6pm UK time, where I'll be sharing something important with you live. pic.twitter.com/qRwf16kw4a

— Ana Ivanovic (@anaivanovic) December 27, 2016

Tennis Australia officials told AAP they were in the dark about Ivanovic’s plans and would be sweating on the announcement with the opening grand slam starting on January 16.

“We will just have to wait and see,” the spokesman said.

The 2008 French Open champion had been scheduled to contest Auckland’s ASB Classic in the New Year before flying into Melbourne for the Australian Open.

Ivanovic also contested this month’s International Premier Tennis League in Asia.

However, her social media post has sparked retirement rumours after a tough 2016.

The injury-plagued Serbian has slumped to world No.63 after winning just 15 matches this year.

She has not been sighted on tour since August after opting to rest wrist and toe complaints following a fifth straight US Open first-round loss.

Ivanovic denied she was considering retirement at the time.

“I just need to really see why is this happening,” she told reporters.

“I had struggles throughout my career. I had some tough times.

“This is not the first time I’m going through this – it just hurts because I know what I invested.”

However, since then she has spoken of her desire to start a family with her husband, Manchester United midfielder Bastian Schweinsteiger.

-AAP