Bolton held the Madrid giants to a scoreless draw to go through to round 16 on a 1-0 aggregate after their 1-0 home win.

"I have great sympathy for any of our supporters who have been injured by what is clearly an overreaction by the Spanish police," chairman Phil Gartside was quoted as saying by BBC Sport.

The Bolton supremo confirmed that he will take the issue to the highest level to get an explanation.

The club said that 17 fans were injured and several others were roughly treated. A fan said: "I've been all over the country watching Bolton and the police in Spain behaved like animals. I have never seen anything like it."

A statement said that Bolton will help the Greater Manchester Police and the British Embassy to gather more information about the incidents.