10/15/2009 at 11:20 AM EDT
Singer Leona Lewis was hit by a fan while signing copies of her autobiography, Dreams,
at a London bookstore Wednesday.
Lewis, 24, had been signing autographs at the bookstore for about 90 minutes when "a guy came up and punched her to the side of the head," the pop star's spokesman tells the BBC. Though she didn't need to go to the hospital, Lewis was "understandably badly shaken," her spokesman says.
On Thursday, Lewis wrote on her Web site
, "Thank you so much for your support it is truly overwhelming. Yesterday was a horrible shock and left me extremely hurt and upset. I’m very sorry to those I wasn’t able to meet at the signing. Thank you again for all of the lovely messages."
A statement was also issued by the singer's rep, who described Lewis as "shocked" but "okay." The spokesman added, "Leona would like us to convey her thanks to you all for your kind messages and your support."
According to an eyewitness at the store in Piccadilly, "[The attacker] walked up there with the book, she signed it and, as she looked up, he just punched her."
"She was running out with her hand over her eye," the eyewitness adds, "and I just saw a man on the floor."
Waterstone's bookstore released a statement about the incident, saying they were supporting any police investigation and thanking Lewis for her professionalism. While the singer did not need to go to the hospital, she did pull out of a scheduled appearance on BBC's The One Show
Lewis recently released
a new single, "Happy," from her sophomore album, Echo
, due Nov. 17.