A man has written an open apology letter to a woman after he scared her by following her down quiet road.

The Reddit user, known by the screen name Karlos, told how he had trailed the woman back towards her parked car near Belfast city centre, leaving her feeling uncomfortable.

'I notice the moment you realised that I was following you by how your pace changed, your shoulders squared and you grabbed your phone,' he wrote.

However the letter took an unexpected turn when the man later revealed the real reason for his actions: he had been trying to protect the woman from two suspicious-looking men loitering on the corner of the dead-end road.

The Reddit user told the story of how he had trailed the woman back to her parked car near Belfast city centre, leaving her feeling uncomfortable. But the tale took an unexpected turn when he revealed there were two suspicious men on the road. Stock image

The man finished the letter, pictured, by explaining that the woman could have been his 'wife or his daughter' and that he couldn't have forgiven himself 'if something had happened'

The post sparked a widespread response from other users, with many praising the poster for being a Good Samaritan.

The letter, titled 'To the girl that I followed today for almost four blocks to her car', was shared on Reddit shortly after the incident at around 4pm last Wednesday.

The man wrote how he had been walking in the opposite direction to the woman when he suddenly turned around and started following 50ft behind her, arousing her suspicions.

He maintained his pace until she turned into a dead-end street where her car was parked and watched as she drove away.

The post sparked a widespread response from other users, with many praising the poster for being a Good Samaritan. Several parents thanked him for looking out for the young woman

But the somewhat sinister tale takes on a fresh perspective when he reveals there were two more men on the street who had gone unnoticed by the woman.

'You probably never noticed was the other two guys, the ones in the other sidewalk, the ones that pointed at you and started to follow you before we crossed the first time, you didn't notice how they looked at you or the fact that they seemed to be on drugs, or a bit drunk, or maybe both,' he posted.

He explained that once she had driven away, he phoned the police and shared photos of the men who had been acting suspiciously.

He finished the letter by explaining that the woman could have been his 'wife or his daughter' and that he couldn't have forgiven himself 'if something had happened and he had done nothing to stop it'.

Some users said the woman was right to be suspicious of the poster, even if his intentions were good. Others said it was a sad reflection on society that there is so much distrust

His post quickly went viral, receiving almost 21,000 likes and mixed views on how he should have reacted.

One mother wrote: 'My daughter is attending school in Belfast.

'She is an international student, out of her element, homesick, and going through some stuff, so being completely aware of her surroundings is probably not her strong suit right now. Hopefully not, but this could have been her. Thank you, even if she doesn't know.'

Agreeing, one user added: 'I have a little sister and people like this just make me so happy. A little less worried every time she’s out.'

Men and women shared their own experiences from both sides of similar situations. Many women said the man was right not to approach as it would only have made her more fearful

However others argued that his actions would have left the woman terrified.

'While I truly appreciate it, I truly do not understand why he didn't just call out to her,' one user questioned.

'Instead of clarifying the situation he pretty much scared the s***out of her and had a picture taken of him by her. I realize yelling out to her may have made the other two dudes act irrationally, but it seems like it that would be a small chance and worth the risk', another said.