"Rehab" pop star Amy Winehouse has been hospitalized for "exhaustion," her rep has announced.

"Amy was admitted to London's University College London Hospital for exhaustion, treated and released just this afternoon," the singer's rep, Tracey Miller, tells PEOPLE. "The doctor said she was suffering from severe exhaustion, and she was told to rest."

The 23-year-old singer's upcoming concerts in Norway and Denmark have been postponed, but the rest of her European dates are scheduled to go on, according to the rep.

"Amy has been pulled in a million directions," added her rep. "She has done hundreds of shows and promotional appearances in the last year, often working 16 hour days. It's bound to catch up with anybody."

Miller says that Winehouse is still expected at the V Festival in Toronto on Sept. 8, at the MTV Video Music Awards on Sept. 9. and to kick off her North American tour on Sept. 12.

Winehouse's hospitalization was first reported by TMZ.com.

It's been a year of highs and lows for the British sensation, who got married in May and whose erratic behavior has grabbed headlines even while her album, Back to Black, has climbed the U.S. pop charts. On Tuesday, Winehouse picked up several MTV Video Music Award nominations for her hit "Rehab," including video of the year, female artist of the year and best new artist.

• Reporting by MARISA LAUDADIO