Troubled retro soul singer Amy Winehouse may have fallen off the wagon again, as she canceled two of her European tour dates following a disastrous (to say the least) performance in Serbia on Saturday.

Winehouse turned in a poor concert in the central/southeast European region, stopping mid-verse, stumbling around the stage, throwing her microphone, relying heavily on backup vocalists, forgetting the words, and looking like she was in a general state of confusion and disorder. All in all, it was a hot mess for the 20,000 fans who turned out to see her. Local media labeled the show the worst in the city's history.

The comeback train (wreck) looks to be derailed before it even left the station. Poor Winehouse. She even checked into rehab for a week, as a pre-emptive measure before she hit the road and things were looking up for her.

The Serbian show, held in the capital city of Belgrade, was to be the first of a 12-date tour this summer for the singer, who has battled substance abuse issues ever since she shot to fame with her much-loved 'Back to Black' album. Instead, Winehouse canceled her show in Istanbul, scheduled for today, and her show in Athens slated for Wednesday. The singer's reps said that the fate of the rest of the Euro dates remains up in the air and that things would be "worked out as soon as possible" regarding a decision on those shows.

Winehouse's next date is scheduled for July 8 in Bilbao, Spain. She has a sprinkling of dates up through Aug. 15 in Bucharest, Romania.

Winehouse apologized to her Turkish and Greek fans, but admitted that she felt the cancelation of dates "is the right thing to do," according to the statement. "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."

UPDATE: Per the label's request, the video of Amy Winehouse getting booed is now unavailable.