The concert late Saturday in the Serbian capital of Belgrade kicked off what was to be a 12-date tour of Europe. But Winehouse decided to cancel appearances in Istanbul on Monday and in Athens on Wednesday, according to a statement from publicity company Outside Organization.
Her representatives said it would be "worked out as soon as possible" whether she would attend the rest of her European tour. The next scheduled concert date after Athens is July 8 in Bilbao, Spain. The tour was to end in Bucharest, Romania, on Aug. 15.
Winehouse would like to say sorry to fans expecting to see her in Turkey and Greece, but "feels that this is the right thing to do," the statement said.
"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," it added.
There was no further explanation for exactly why Winehouse was canceling.
But Winehouse, who has publicly struggled for years with drug and alcohol issues, was jeered as she performed in Belgrade. She arrived almost an hour late before stumbling to the stage and appearing unable to remember the lyrics to her songs. She dropped the microphone, mumbled through her songs and occasionally disappeared, leaving her band to keep on playing.
Serbian media described the concert before 20,000 fans as a "scandal" and a "disaster." The Blic daily said the concert was "the worst in the history of Belgrade."
The crowd at Belgrade's Kalemegdan Park could hardly tell which song Winehouse was singing and responded angrily. Many walked out in disappointment.
"It was horrible," said Ivana Bilic. "She should have canceled the whole thing, rather than appear at all like this."
The Daily Blic posted a clip from the concert on its website, commenting, "Listen if you dare."
Tickets cost about euro40 ($57) -- very expensive in the country where average salaries are about euro300 ($428) a month.
Winehouse recently spent a week at a rehab program in London. Her 2006 breakthrough album "Back to Black" won five Grammy Awards, but her music in recent years has been overshadowed by her drug use and run-ins with the law.