R&B star Rihanna is facing legal action from her former head of security over allegations of defamation.

Geoffrey Keating, from Dublin, filed suit against the Stay hitmaker in Ireland's High Court on Monday (28Apr14), accusing the singer of making "nauseatingly offensive" and false statements about him in an email exchange last July (13).

Details about the insults in question have not been revealed, but Keating claims the allegations caused serious damage to his reputation and cost him lucrative business.

His attorney, Gerald Kean, has been granted permission to serve the star, real name Robyn Rihanna Fenty, with the legal papers at her home in New York, where she was spotted attending the Brooklyn Nets basketball play-off games over the weekend (25-27Apr14).

Kean tells Tmz.com, "We're taking this battle very seriously. We are satisfied that the Irish Courts will see justice at the end of the day."

Keating, who is demanding undisclosed damages, served as Rihanna's head of security on her Diamonds World Tour between October, 2012 and July, 2013.