06/21/2011 at 07:05 AM EDT
's current European tour, which was to have included 12 stops before winding up Aug. 15 in Bucharest, Romania, has been canceled, it was announced Tuesday morning.
The problem began Saturday night. Attempting to perform while appearing to be under the influence, Winehouse was booed in Belgrade after arriving on stage an hour late, then stumbling around and slurring the words to her 2008 song "Just Friends."
She greeted the crowd of 20,000 by shouting, "Hello, Athens," reports the U.K.'s Telegraph
Following the incident, Winehouse, 27, apologized to fans and canceled Monday's scheduled performance in Istanbul and Wednesday's in Athens.
Late last month, Winehouse checked into rehab
for her ongoing problem
with alcohol, the singer's rep confirmed to PEOPLE. The treatment was seen as preparation for this tour.
In a statement following the Belgrade incident, Winehouse's management 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. … She would like to apologize to fans expecting to see her at the shows but feels that this is the right thing to do."