Bell, 25, is the star of the current blockbuster "The Adventures of Tintin." He is best known for his work in the movie version of "Billy Elliott."
Wood, 24, is a member of the cast of TV's "True Blood."
UsMagazine.com published a photo taken Saturday of the couple with Wood wearing a dazzling new ring, but the celebrity news Web site said Wood's representative declined to comment on its report.
Bell and Wood met in 2005 and dated for a year starting in 2006, then broke up and reconciled last summer. Wood was previously engaged to shock rocker Marilyn Manson.