On Friday, Sept. 11, Kelly Clarkson took to Twitter to announce the cancellation of her six upcoming "Piece by Piece" concert tour dates, Entertainment Tonight reports.

Clarkson revealed that she recently had a doctor's visit, at which she was advised to go on vocal rest due to severe vocal strain she developed over the course of her tour.

ET notes that the "American Idol" alum was very apologetic to her fans, and promised to get "back on the road" and sing again once her vocal chords become healthy.

Clarkson also assured her fans who already purchased tickets for her cancelled shows that they would be issued full refunds.

Check out some of Clarkson's tweets below.

People reports that Clarkson's cancelled tour dates started as early as Sept. 12 and will continue through Sept. 20. The cancelled shows included two shows in Vienna, Virginia and one show each in Tampa and West Palm Beach, Florida; Raleigh, North Carolina; and Camden, New Jersey.

Clarkson's "Piece by Piece" tour has been widely successful, according to People. She's had multiple sold out shows in various cities, and fans have praised Clarkson for singing covers of popular songs, such as Prince's "Purple Rain," Taylor Swift's "Blank Space," and NSYNC's "Bye, Bye, Bye."

ET reports that prior to her latest vocal scare, Clarkson lost her voice back in June after the birth of her daughter River Rose. During that time, Clarkson expressed her fear that her singing career was over.

"Afterwards was the part where I literally had a moment where I cried and drank wine all day," she admitted to ET. "I was like, 'Oh, God, I'm not going to be a singer anymore!' I was bawling to my husband and like, completely hammered, just going, 'Oh my God, it's over, I don't know what I'm going to do. I guess I could do more charity work.' Like, I didn't know what I was going to do."