Winehouse, 27, struggled to perform her songs and keep her balance at the gig in the Serbian capital Belgrade, and on some tunes the audience did most of the singing.

"Amy Winehouse is withdrawing from all scheduled performances," a spokesman said on Tuesday.

"Everyone involved wishes to do everything they can to help her return to her best and she will be given as long as it takes for this to happen."

The Grammy-winning, chart-topping singer of hits including "Rehab" and "Love is a Losing Game" had been due to perform a series of European dates including Athens on Wednesday and Bilbao on July 8.

The tour had been scheduled to wind up on August 4 in Portugal

The news is a major setback for the artist and her entourage. Only three weeks ago she checked out of a rehab clinic and confidently looked forward to her upcoming tour.

Winehouse, who has struggled with addiction throughout her career, rose to fame in 2006 with hit single "Rehab" and won four Grammys awards in 2008 including best new artist and album of the year.

She was unable to attend the ceremony in Los Angeles because of legal problems, and she is yet to release a follow-up recording.

Copyright Reuters, 2011