RILEY CHANGES THE LOCKS!

With their court battle over the family trust just weeks away, the Presleys up the ante

The Presley family feud has taken another nasty turn after Riley Keough reportedly locked her grandmother Priscilla Presley out of Elvis' famous estate Graceland!

A Hollywood insider claimed the 77-year-old actress recently visited the Memphis mansion to discover Riley had "changed the locks on the upstairs doors and archives".

According to the source, before Riley, 33, was made the sole executor of late mother Lisa Marie Presley's will following her death in January, "Graceland archives director Angie Marchese, Priscilla and Lisa Marie had the only keys. So Priscilla is now locked out - and she's furious!"

While a spokesperson shot down the claims, insisting, "No locks at Graceland have been changed since Lisa Marie's passing," the war between Riley and Priscilla certainly rages on.

Sources say the pair - who are due in court on April 13 for the next hearing in their fight over the family trust - are now only communicating through lawyers. And it seems Priscilla will have an ally in court - her former son-in-law Michael Lockwood.

The 61-year-old guitarist has filed legal papers requesting a judge allow him to represent his and Lisa Marie's 14-year-old twins Harper and Finley in the legal battle.

Priscilla's ongoing relationship with Michael - who Lisa Marie falsely accused of possessing child pornography during their lengthy child custody battle - was a major sticking point between Priscilla and her late daughter.