Dozens of Foxes fans had gathered in the iconic central square in Madrid and they clashed with officers when riot police were called in at around 10pm to clear the plaza.
Madrid authorities confirmed that eight fans had been arrested and that two police officers were slightly injured as well as two fans who were treated at the scene.
But eye-witnesses claim police were heavy handed with “good natured” supporters who were enjoying a night out in Madrid ahead of the Wednesday match against Atletico Madrid.
Mr Mackie told BBC 5 Live the trouble happened after fans had been told they would be allowed to gather in the Plaza Mayor.
He said: “I got down [to Plaza Mayor] and found a number of young Leicester fans with bruises, who had been hit on the head, arms, knees and a couple of them dazed. Some of them drunk as well.
“As I was talking to them there was a charge. Police officers just charged a group of Leicester fans who were, as far as I could tell, just walking past and chatting to each other.
“Three of them were pushed to the floor and hit with batons and bundled into the back of vans and taken away.”
— Phil Mackie (@philmackie) April 11, 2017
But Spanish sports daily AS was sent footage of Leicester fans raiding a cafeteria on a train bound for Madrid and stealing cans of beer while chanting “It’s fucking free”.