They know that she's no good... Amy Winehouse booed off stage in Serbia

The concert that was supposed to begin the comeback tour for Amy Winehouse turned into a fiasco on Saturday night when the troubled singer came on stage in Belgrade apparently too drunk to perform.

A chorus of boos and a hail of paper cups from the 20,000-strong crowd greeted the "Rehab" singer's abortive performance, which seemed to suggest that her efforts to stay on the wagon after a recent stint in the Priory have ended in failure. She appeared consistently unable to recall the lyrics of her songs, or to sing those she could remember with any clarity, instead mumbling her way through hits like "Valerie" and "Just Friends". She was even unable to speak coherently.

Nearly half of the agonising, 71-minute show consisted of an attempt to introduce the members of her bemused band which appeared to be stymied by her inability to remember their names. She was likewise unclear about her location, first greeting the audience "in Athens" and then "in New York".

The anger of the crowd, which had waited patiently in Belgrade's 34C heat until 11pm for Winehouse to perform, was clearly visible. Some 3,000 had come from neighbouring Bosnia, Croatia, Hungary and Macedonia to see the star. "She promised to sing some new songs in Belgrade," said Macedonian Emil Vlaskovski, 24. "But God, she could not sing old ones or remain on her feet."

And Jana Markovic, 20, from the Croatian town of Vinkovci, said: "That was not singing. She was mumbling and holding her hand before her mouth. I'm really mad as I don't know why I paid ¤40 (£35) to see that." Belgrade resident Zarko Stojcevic said the artist seemed to be "stumbling drunk".

Ms Winehouse's difficulties were visible from the start of the show, as she stumbled on to the stage, took her shoes off and fell over. She said she was 'the happiest girl in the world" at one point, but within a minute she had thrown her microphone down and disappeared into the wings. She repeated such exits several times, as her band – which many fans said were the heroes of the evening – tried to fill in. While attempting to sing "Back to Black", Winehouse struggled to follow the rhythm of the band, who slowed the tempo almost to standstill to help her.

The concert, at the stunning medieval Kalemegdan fortress, had been intended to mark a new beginning for the singer after she checked out of the Priory clinic earlier this month, where she had been treated for her drinking. When she checked out, her spokesman had said that, while she would continue as an outpatient, "she is now looking forward to playing shows around Europe this summer and is raring to go".

Following the diststrous performance in Belgrade, a spokseperson for Ms Winehouse announced last night that she had cancelled concerts in Istanbul tonight and in Athens on Wednesday. No decision has been taken on the rest of the 12 date European Tour.

She has not released an album since 2006's acclaimed Back to Black. In 2009, her record label's co-president said that her new material had "absolutely floored" him and that a follow-up record would be released in 2010. But that has still not materialised.