Christina Perri Fights Off Carjacker

Law enforcement sources tell TMZ ... Perri called police early Friday morning claiming she was behind the wheel of her car, waiting to pull into a L.A. building around 2 AM ... when an unknown male approached her vehicle and opened the driver's side door.

Perri claims the man instructed her to "move over" and tried to shove himself into the car -- but she wouldn't budge ... and a struggle ensued.

Perri told cops she fought the man off ... and began honking the horn to attract attention.

The suspect eventually ran away ... but not before allegedly striking Perri in the head and body a few times during the altercation. Perri said she did not need immediate medical attention

Cops responded -- and are now investigating the situation. So far, cops have not identified a suspect.