Lindsay Lohan -- Cops Called to L.A. Home Over Rogue Door Knocker

Cops were called to Lindsay Lohan's Venice Beach pad earlier this evening -- after a strange, unidentified man came a-knockin' ... and Lindsay freaked the hell out.

Law enforcement sources tell TMZ, the man -- an older gentleman -- arrived at her home around 6:30pm and began knocking on the front door.

We're told Lindsay came to the door and asked what he wanted -- and the man responded cryptically ... that he needed to speak with her.

Unnerved, Lindsay asked the man to leave, but he refused, demanding she open the door. Police received a call minutes later about a trespasser on Lindsay's property. It's unclear if Lindsay made the call.