Celtic fans could be in for a nightmare next away day in the Champions League with Borussia Dortmund launching an official protest to UEFA after their fans complained they were strip-searched and manhandled before their game at Dinamo Zagreb.

The Hoops travel to Croatia next month in their next game in the competition after a draw against Club Brugge this week at Parkhead.

But their fans will be wary after Dortmund fans lashed out at excessive searches before their match, where the Germans romped to a 3-0 win.

BVB had 2,500 fans in Zagreb, but they were astonished when the Croatian security forces ordered them into tents set up near the turnstiles where they were ordered to strip completely to check for pyrotechnics or prohibited items.

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Fans also complained about the way they were treated by the local security forces, with male supporters even reporting they were subject to their 'genitalia being forcibly grabbed by police and security staff' during the search, according to German media reports.

Dortmund fans were so outraged at their pre-match treatment they even considered boycotting the game entirely before deciding to enter the Maksimir Stadium.

The club have now made an official protest to UEFA.

Sports director Sebastian Kehl said: "There was clearly a lot of unrest outside the stadium before the game."

Dortmund then released a statement which said: "We have received numerous complaints about the security service's actions during the personal checks during the admission phase.

"We condemn this form of checks and are currently in contact with UEFA and Dinamo Zagreb to report and investigate the incidents. Other affected fans should please contact our fan representatives."

UEFA had already designated the match a high-risk fixture and yet despite the extreme searches before the game, Dortmund fans still managed to produce a pyro display in the second half of the game.