Katy Perry is locked in a real estate battle with a group of nuns.

The 'Roar' hitmaker is reportedly keen to snap up the hilltop property in Los Angeles for over $14 million after securing a deal with Archbishop Jose Gomez.

However, the five sisters of the convent are believed to have sorted their own sale on the property to businessman Dana Hollister - who wants to turn it into a boutique hotel - for $1 million more than Katy offered.

The nuns and the Archbishop are now said to be battling over who owns the rights to the building.

Katy reportedly visited the nuns to try and win them over with a gospel rendition of 'Oh Happy Day' as well as proving her commitment to the faith by showing off her religious wrist tattoo.

Of their meeting, Sister Rita Callanan told TODAY: ''Our days have not been happy since then, I can assure you.''

The nuns also felt it was necessary for the group to find out who Katy Perry was, so they tuned into her Super Bowl half time show earlier this year.

Speaking of Katy's performance - where she flew over the stadium atop a shooting star - Sister Rita said: ''I thought, is that a way to make money?

''Maybe I could fly around. I could be the flying nun.''