The Disney actress and singer has been strongly rumoured to be dating teen heartthrob Justin after they were pictured together on a tourbus in Florida last month and, more recently, in the Caribbean.
One picture showed what appeared to be Selena, 18, wrapped in a towel with Justin, 16, kissing her on the cheek.
Angry fans of `Baby` singer Justin have now taking to twitter to threaten his rumoured girlfriend on twitter.
One posted: "I`ll kill you I swear on GOD!!!!(sic)"
Another angry fan wrote: "If you are the Girlfriend of Justin I will Kill you I HATE YOU :@ !!!(sic)"
Yet another vitriolic message aimed at Selena read: "w***e cancer w***e. Iike i`m kill myself cuz i saw you and Justin kissing well thankyou Selena thankyou now i`m killing myself (sic)."
It is not known at present if Selena has sought any protection from the threats or if she has sought to get the people responsible for the tweets banned from the social networking site. She and Justin have also previously denied they are in a relationship together.
Other fans of Justin - who call themselves Beliebers - have taken a more mild approach and wished the possible couple well, however, with one posting: "If you really are a BELIEBER, no matter what Justin Bieber do, you`ll support him until the end. That`s what you call a fan (sic)."
Another poster wrote: "SelenaGomez is way too awesome for Justin Bieber."
Last year reality TV star Kim Kardashian was also subjected to a similar negative backlash after she posed for racy photos with Justin.