Jessica Biel, Gerard Butler 'on romantic bike ride'

Jessica Biel's motorcycle ride with Gerard Butler has sparked suggestions that the pair have begun dating.

The stars met while filming director Gabriele Muccino's upcoming film Playing the Field, the comic tale of a former professional athlete who must balance coaching his son's soccer team with his attraction to several of the players' mothers.

Biel was spotted gripping Butler tightly over the weekend as they drove down the Pacific Coast Highway on a Harley Davidson bike, a source told the New York Post's Page Six.

Reps for both Biel and Butler have denied that the pair are romantically involved.

Biel, 29, was recently praised by former boyfriend Justin Timberlake for being the "most significant" person in his life.

Butler claimed last year that he prefers to keep his romantic relationships hidden from the media in order to maintain his privacy.

Playing the Field, which also stars Catherine Zeta-Jones and Uma Thurman, is currently scheduled to be released next year.