TORONTO, Canada (AFP) - Toronto police on Friday denied heavy-handed tactics were to blame for ugly clashes between officers and members of Chile's Under-20 football team.

The Chilean team fought with police and security officers after a 3-0 semi-final loss to Argentina at the FIFA Under-20 World Cup tournament here on Thursday night.

On Friday, the trouble threatened to become a diplomatic incident.

The South Americans accused police of using pepper spray and electric-shock guns against their players, with Chile's Minister of Foreign Affairs Alejandro Foxley calling for a formal explanation from the Canadian government.

But police chief William Blair insisted that the incident was provoked by the Chilean team who were furious with the referee's decisions during the match, which left them with nine players against Argentina's 11.

Several Chilean players angrily confronted the referee on the pitch afterwards and outside the stadium there was an altercation between police and the footballers as they headed toward their bus.

Television showed some players handcuffed and all 21 Chilean players were detained briefly by police.

"Things got heated during and after the match and the Chilean team, apparently angered by the referee and frustrated at losing clashed with our officers," Blair said in a statement.

"My officers were forced to intervene to protect the refereeing team in the first instance. Then when the two teams were leaving the stadium, a member of the Chilean delegation and an Argentinian fan exchanged words. Once again we had to intervene.

"The Chileans turned the violence towards our officers. Their role was to respond firmly but fairly. They were dragged into it and they applied what they had learned.

"We're going to study this incident in detail to ensure that it does not happen again between now and the end of the competition."

Chile's Minister of Foreign Affairs on Friday demanded an explanation.

"We've decided to send a note through our ambassador in Canada to the Canadian Ministry of Foreign Affairs to convey to him the unease felt in Chile regarding what happened, the excessive violence, and to demand a formal explanation - which I hope will be detailed," Alejandro Foxley told the press.

World football governing body FIFA have opened an inquiry into the affair.