Leicester fans have been been filmed chanting 'Gibraltar is ours' in Madrid.
The Foxes are in the Spanish capital for their Champions League quarter-final first leg with Atletico.
A large section of supporters gathered in the Plaza Mayor Square ahead of the match at the Vicente Calderon.
Hours before kick-off tensions spilled over as fans clashed with local police.
Flares and bottles were thrown during the ugly incident with police using batons to quell the disorder.
Leicester fans were heard chanting 'You Spanish b******s, Gibraltar is ours."
A number of arrests were reportedly made following the incidents
The scenes follow clashes between Leicester fans and local police on Tuesday night, which saw eight arrested.
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Meanwhile, Leicester fans have claimed tear gas and rubber bullets were fired at them by police.
Emma Chetwynd from Tamworth alleged: "We did scarper out quite quickly when the police decided to throw rubber bullets at us. It was provoked but it did get a bit tasty so we left.
"There were five or six big bangs and everyone was saying it was rubber bullets but we left quite quickly.
"It started with a bit of trouble from our fans but they (police) didn't need an excuse to blast in. It's any excuse - it's hard to say - but any excuse and they'll come in.
"A few people we saw who haven't been causing trouble have tried to talk to them but they were rudely brushed away."
Earlier, Spanish police reportedly said eight Leicester fans were arrested for "causing a mess" on Tuesday night.
Clive Langley, who travelled with son Paul, was in the Plaza minutes before the incident on Wednesday and felt the tension was building, alleging that tear gas was used.
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He said: "I could see what was about to happen so I said 'let's go and get something to eat'. Sure enough about 10 minutes later it was tear gas and 'whack, whack whack'. We didn't see rubber bullets but certainly tear gas."
However, another Leicester fan, Rak Singh from Oadby, felt any trouble was blown out of proportion.
He said: "They come in and clear out but nothing was happening."