Former women's world number one Kim Clijsters has retired from competitive tennis for the third time in her career, she announced on Tuesday.

The Belgian, a four-time Grand Slam champion, returned to the WTA Tour in February 2020, but her comeback coincided largely with the Covid pandemic and she played just five matches.

"I want to share with you that I have decided to no longer play official tournaments," Clijsters wrote on Instagram.

"I can't wait to see what new adventures will cross my path. Thank you to everyone who has supported me over the past two years!"

The 38-year-old, who won the 2005 US Open, originally retired in 2007 to start a family, before returning to the tour two years later.

Clijsters went on to win another three Grand Slam titles -- consecutive US Opens in 2009 and 2010 and the 2011 Australian Open -- before hanging up her racket again in 2012.

She struggled on her second return, though, failing to notch a match win.

But Clijsters, who was world number one on four different occasions, said she has no regrets.

"I think my determination was something as a little girl that was a huge factor," Clijsters told the WTA website. "This is something that came from my parents –- they always pushed me in believing, 'OK, what you do for your sport, you have to do it 100 percent'...

"And out of everything, that's probably what I'm most proud of –- that I really did that. From the moment I stepped on court and, whether it was practice or a match, I was committed. I was there to try my best."

Her final WTA match was a three-set loss to Katerina Siniakova at Indian Wells last October.

Clijsters won 41 WTA singles titles, including the season-ending Tour Finals in 2002, 2003 and 2010.