Los Angeles, 3 March 2011 | AFP

Update 12:50 pm. Serena Williams, a former world number one and 13-time Grand Slam singles champion, is well and was recovering at home on Wednesday after emergency surgery on Monday to remove a blood clot from her lungs.

Williams suffered a pulmonary embolism last week and a second health scare that required her to undergo an emergency operation at Cedars-Sinai Medical Center in Los Angeles on Monday, said Williams representative Nicole Chabot.

The 29-year-old American tennis star issued a statement on Wednesday that said she was at home recovering but under strict doctor’s supervision and with no idea when she might return to the sport she once dominated.

“This has been extremely hard, scary, and disappointing,” Williams said. “I am doing better. I’m at home now and working with my doctors to keep everything under control.

“I know I will be OK but am praying and hoping this will all be behind me soon.

“While I can’t make any promises now on my return, I hope to be back by early summer. That said, my main goal is to make sure I get there safely.”

As fans and rivals worldwide began to worry about Williams and her health, her mother, Oracene Price, posted a note on the social network Twitter saying, “Thank you for your concern. She is fine.”

Williams underwent surgery a day after she attended post-Oscar parties in Hollywood.

“Monday Serena Williams underwent emergency treatment at Cedars for a hematoma she suffered as a result of treatment for a more critical situation,” Chabot told People magazine.

“Last week, Serena suffered from a pulmonary embolism which was discovered upon her return to L.A. She had been in New York for doctor appointments for the ongoing issues with her foot.”

Williams, who has slid to 11th in the rankings, has undergone two operations on her right foot since it was cut by glass at a restaurant last July. She has not played a top-level match since taking last year’s Wimbledon title.

In a Twitter message just after midnight on Wednesday, Williams posted the note “Tough day”.

The news about Williams was a stunner to world number two Kim Clijsters, the reigning two-time US Open champion who tweeted, “Just read about Serena!!!! Very scary, hope she is ok!fingers crossed!”

Williams, who ranks sixth among women on the all-time grand slam singles title list, has won the US Open in 1999, 2002 and 2008, Wimbledon in 2002, 2003 and the past two years, the French Open in 2002 and the Australian Open in 2003, 2005, 2007, 2009 and 2010.

The younger sister of fellow tennis star Venus Williams, Serena Williams stretched her stay atop the world rankings to 123 weeks before her limited play contributed to Caroline Wozniacki passing her for No.1 last October 11.

The Williams sisters, 12-0 together in grand slam doubles finals, were to have played on the US Fed Cup team in last year’s final against Italy but pulled out due to injuries.

Serena and Venus Williams must play in the Fed Cup this year and next in order to be eligible for selection to the US Olympic team for the 2012 London Olympics.

A right hip injury forced Venus Williams to retire from a third-round match at the Australian Open in January and she has not played since.