Germany's top-ranked tennis player Andrea Petkovic has pulled out of next week's Australian Open Grand Slam tournament with a stress fracture, organisers said on Wednesday.

"Don't like to be the bearer of bad news, but Petkovic has withdrawn," tournament director Craig Tiley tweeted.

Tenth seed Petkovic's withdrawal came shortly after seven-times Grand Slam winner Venus Williams pulled out, also citing health reasons.

Williams has been receiving treatment for Sjogren's syndrome, an auto-immune disease that causes fatigue and joint soreness.