An elderly couple who opened their front door on Monday night to find a badly bashed, naked man pleading for help say they called triple-0 and covered the man with a blanket because of their Christian faith.

Police have hailed the pair as good Samaritans for helping the man when he staggered onto their front porch, covered in blood and barely coherent.

Cry for help: The man pressed on the bell at this house. Credit:Rachel Olding

He told police that he had been mugged, stripped, tied up and locked in a car boot.

The man, who police are yet to formally identify and who speaks little English, desperately pressed on the front door bell of the Liverpool couple's home dozens of times at 8.45pm screaming "help me, help me".