Spanish police fought with players from Peru's national football team in astonishing scenes outside a Madrid hotel.
The footballers were trying to greet fans waiting for them when the violent scuffle started.
Local reports blamed the fracas on the fact some of the officers failed to recognize the stars as professional footballers and confused them with supporters in the bust-up.
A Peruvian fan could be overheard shouting: 'Calm down, calm down, they're players' as tempers flared and the pushing and shoving threatened to boil over into a full-scale punch-up.
Goalkeeper and captain Pedro Gallese, who plays his club football for Major League Soccer club Orlando City, complained in the aftermath of the fracas: 'We wanted to greet the fans and they began to punch us.'
The incident occurred on Monday as the Peruvian team reached the hotel where they were staying after their last training session ahead of Tuesday night's friendly against Morocco in Atletico Madrid's Wanda Metropolitano stadium.
It was not immediately clear on Tuesday morning if there had been any arrests, although Peru's goalkeeper could be seen showing off his torn top as he was pushed back towards the hotel entrance moments after he became caught up in the violent confrontation.
The Peruvian Football Federation said in a statement overnight: 'We regret the incidents that occurred in Madrid where fans of the team had gathered traditionally to wave flags.
'The Peruvian Football Federation is supportive and backs our player and captain Pedro Gallese and has accompanied him since the incident occurred outside the hotel where the team was staying ahead of their friendly against Morocco.
'We reiterate that we are respectful of the authorities and the procedures of each country that we visit.
'For this reason, we are at the full disposal of both the internal and external enforcement authorities and supervisory bodies to try to clarify what occurred.'
Urging their fans not to react inappropriately in the coming hours, the federation added: 'We call on them to remain calm and we express our firm rejection of violence.'
A spokesman for Spain's National Police confirmed a Peru player had been arrested for allegedly hitting an officer in the eye.
The spokesman said he could not confirm local reports the arrested man was 33-year-old goalkeeper Pedro Gallese, who was said to have been released after being taken to a nearby station for questioning.
The incidents happened outside the NH Collection Eurobuilding.
He added: 'Around 300 fans started gathering outside from about 7 pm onwards.
'Some began to let off flares and officers from a rapid response unit called the UIP were called in as backup.
'Just before 10 pm local time the players arrived.
'The fans tried to reach the players and the police got in the middle between the players and the fans to avoid an avalanche of people endangering public safety.
'A player was arrested for hitting an officer in the eye. He was taken to a n