The superstar launched her world tour on 31 August (15) in Canada, and she has been performing shows in the U.S. since September (15). The tour, her first since 2011, coincides with the release of her latest album Unbreakable, which recently topped the Billboard 200 chart.

However, Janet announced on Twitter.com on Friday (23Oct15) that she is rescheduling two dates - Salt Lake City, Utah on 24 October (15) and Denver, Colorado on 25 October (15).

"Hey you guys, I must rest my vocal chords (sic). Doctor's orders..." she writes. "Will be rescheduling Salt Lake and Denver. Keep your tickets! Back to Burn Up Kansas City. Gon B Alright (sic). #Unbreakable."

The star made headlines on Thursday (22Oct15) after her management team took down fan footage of her concerts from Instagram.com, and even had some user accounts suspended.

Janet later told her fans that while she appreciates them posting videos online, her team was "protecting the intellectual property we are creating for the tour and possible future projects."

She added that she had asked her team to "change their approach" and allow fans to resume posting videos.