An angry post-match confrontation between Chilean soccer players and Toronto police has escalated to become an international incident, with officials in Santiago laying the blame squarely on Canadian authorities.

Chilean President Michelle Bachelet told local reporters she was dismayed with the use of "unjustified aggression" by Toronto police after a bloody brawl following a FIFA U-20 World Cup match late Thursday.

"In our judgment, what happened was particularly serious because the Chilean delegation suffered unjustified aggression," she said.

Her government is lodging a formal complaint with Canadian Foreign Affairs Minister Peter MacKay to demand an explanation for why police used "such unusual methods'' to deal with the situation.

But Canadian Prime Minister Stephen Harper, who just visited Chile a few days ago, said only that "international soccer matches are hotly contested and often become very emotional."

He added that "There are processes in Canada by which the authorities review these kinds of things and I don't intend to comment any further."

Toronto police say they were responding to aggressive behaviour with necessary force.

At a packed press conference on Friday, Chilean Football Federation President Harold Mayne-Nicholls apologized for the behaviour of the team, but slammed the police response.

"I personally saw that the police of Toronto did not act as our police is used to acting with people that are just playing a football game,'' said Mayne-Nicholls.

"For us, as the chairman of the Football Federation of Chile, we cannot accept those kind of things coming from the police. Our players are 19-year-old, 20-year-old kids. They were playing football and they never deserved the treatment they were receiving.''

Mayne-Nicholls wouldn't say what prompted the fight, only that the players were relaxed in the changing room after the match.

"I'm sure they are completely innocent on this but I want to know exactly what happened,'' he said.

Mayne-Nicholls told reporters that the Federation is waiting for a final report to learn exactly what transpired.

Despite the friction, the president of the Chilean Football Federation assured media the players were prepared for their match against Austria for the third-place spot on Sunday.

The consul general of Chile also weighed in on Friday, saying Toronto police need to do more than just apologize for Thursday night's brawl with members of the Chilean FIFA U-20 soccer team.

Apology not enough

"I don't think a mere apology would be enough, I don't think so," said Ricardo Plaza. "Clearly something much more serious needs to be done. This is a serious problem and it needs a serious solution.

Speaking with CTV News, Plaza said police were rude to him when he showed up at the stadium after learning of the scuffle that took place outside the National Soccer Stadium.

He accused the police of using excessive force with the players, all of whom are under the age of 20. Instead of protecting the players, they attacked them, he said.

"They used extreme, excessive force, not used in appropriate way," he said. "I can't understand how they could react in such a way. It's not understandable and it's unacceptable."

Tensions erupt

Tensions between the two teams competing in the FIFA U-20 World Cup semi-final reached a boiling point after Chile lost to Argentina 3-0.

German referee Wolfgang Stark called 53 fouls -- 30 against Chile. Two of their members were eventually ejected during the game.

During the game, nine yellow cards were issued to the team while two yellow cards were issued to the opposing Argentina team. A yellow card is considered a serious warning -- two of them in a single game and the player is shown a red card, which means ejection.

Emotions were running high among players, angry at what they said were unfair calls by referees.

When the final whistle blew and Chile had been shut out 3-0, the team started to go after the referees, egged on by an angry public audience. However, police ushered the refs away to the tunnels underneath the stands.

Later outside the stadium, an altercation erupted between police and athletes as they headed to their bus.

A reporter with The Canadian Press said he heard people yelling near the Chilean team bus after the game. A scuffle then broke out between four or five people, and quickly escalated.

'A big dogfight'

"Next thing you know, the bus just unloads and there's eight, 10 players come off the bus and there's just fists flying everywhere, between the cops, the security guards, a couple of ladies were involved that were security," said reporter Nathan Denette.

"It looked like a big dogfight. People throwing fists and cops with their billyclubs out and then all of a sudden it got out of control."

A police officer then used a Taser to subdue one of the people in the melee, though it was unclear if he was a player or an official with the Chilean team.

"As soon as that happened, it got even worse," Denette said.

Hundreds of angry and chanting fans were kept at a distance, separated by a fence as FIFA and Canadian officials looked on in shock.

Police soon got a handle on the situation, handcuffing team members, many of them bloodied and screaming, and escorting them back into the dressing room where they remained detained for several hours.

"They hit me with an electrical current and I fainted,'' player Isaias Perralta told Chilean media. "When I regained consciousness, I saw 10 police officers were hitting me and throwing acid in my face.''

All 21 players from the Chilean under-20 soccer team were detained by police.

Eventually, police let them all go without making a single arrest.

"All (Chilean) players have been released from custody of the police to care of the Chilean delegation,'' FIFA spokesman John Schumacher said. "The Chilean players were detained by the police to de-escalate the situation that was taking place in front of the stadium."

"The entire situation is under investigation by FIFA, the LOC (local organizing committee), the police authorities in Toronto as well as the Chilean delegation,'" he continued.

FIFA President Sepp Blatter told reporters at a press conference on Friday that the association had asked the relevant authorities in Toronto to report details of their probe back to his organization.

Police reaction

Toronto Police Chief William Blair released a statement Friday outlining what happened.

"My officers were forced to intervene, initially, to protect the referees. As the teams were leaving the stadium, an argument broke out between a member of the Chilean team and a rival fan," he said. "My officers were forced to intervene, again, to end the dispute. Members of the Chilean team then decided to direct some of their aggressive behaviour towards my officers."

Blair said the officers did what they had to do to control the situation.

"The job of my officers was to respond in a firm, but fair, manner to end that violence. They are trained to do so, and that is what they did," he said.

"We will look, in detail, into what happened last night to see what changes, if any, we need to make to the policing arrangements for Sunday's matches."

There are no plans to investigate the matter further, although police may respond to the allegations levelled against them, said Toronto police spokesman Const. George Schuurman.

"As far as I know, it's a case closed,'' he said.

"It happened last night, people were arrested, they were investigated, they were released, no charges -- and that's the end of it.''

Toronto Mayor David Miller called the incident "regretful" considering the tremendous success of the games so far.

However, he wouldn't comment on the behaviour of the police force.

"Until the police investigation is complete, I can't comment on any action police took," he said.

"I do know the inspector in charge showed tremendous good sense to return all players to the custody of their coach.

'Upset with the ref'

"The players were upset. They're young players,'' Chile coach Jose Sulantay said at a post-match press conference through an interpreter, referring to the melee on the playing field after the final whistle. "The red card affected them."

"The coaching staff tried to calm them down, but they were upset with the ref and the red cards.''

While Sulantay explained away his players' frustration to reporters, the brawl was breaking out outside the stadium.

Chile is expected to play Austria Sunday for a third-place finish before the finals between Argentina and Czech Republic.

Plaza said he hopes the team will recover from Thursday night's incident in time for the game.

"I hope they will recover and will be assisted and will be able to play on Sunday as if nothing happened," he said. "It will be very difficult. They will have the incident in the back of their minds."

The under-20 competition is FIFA's largest tournament after the World Cup. The organization was congratulated for setting record ticket sales for the tournament at BMO Field.

The field is being dubbed the National Soccer Stadium during the tournament because of issues around sponsorship.