(CNN) -- Amy Winehouse's attempt at a European concert tour ended in Belgrade, Serbia, with a train wreck of a performance Saturday night in which she staggered around the stage and stumbled through several songs.
The audience eventually chased Winehouse off the stage with loud boos several numbers into what was supposed to be the opening show in a 12-date tour.
A representative for Winehouse said her next two concert dates have been canceled.
Winehouse representative Tracey Miller did not directly confirm that the "Rehab" singer, who has a history of battling drugs and alcohol, had fallen off the wagon. Winehouse only recently left a British rehab program that a representative said was intended to prepare her for the European concerts.
"Yes, Amy has cancelled appearances in Istanbul and Athens for the coming week," Miller told CNN Sunday. "Despite feeling sure that she wanted to fulfill these commitments, she has agreed with management that she cannot perform to the best of her ability and will return home."
Video clips of the musical disaster, recorded by concert-goers' cell phone cameras, were quickly posted on YouTube. They showed Winehouse failing in every attempt to sing more than a few slurred lines of her songs. Audience members could be heard filling in the gaps, along with her back-up singers.
"She would like to apologize to fans expecting to see her at the shows but feels that this is the right thing to do," Miller said.
When Winehouse entered a rehab program at London's Priory Clinic last month, a representative told CNN that "she wants to be ready for performances in Europe this summer and decided to seek an assessment."
CNN's Denise Quan contributed to this report.