Twelve matches in the Europa League and three in the Champions League are among "around 200" games being looked at by UEFA as part of an investigation into alleged match-fixing described by one official as the biggest to ever affect European football.

European football's governing body confirmed on Friday the majority of the games under investigation are domestic league matches in nine countries.

German authorities confirmed 32 matches in Germany were under suspicion, including four in the second division, with the remainder in lower leagues.

Matches in Belgium, Switzerland, Croatia, Slovenia, Turkey, Hungary, Bosnia-Herzegovina and Austria are also believed to be under investigation.

UEFA revealed the 15 European matches concerned are all early qualifying round games.

Peter Limacher, UEFA's head of disciplinary services, told a press conference in Germany: "This is undoubtedly the biggest fraud scandal there has ever been in European football.

"We are deeply shocked by the extent of the match manipulations by international gangs.

"We now have to do everything we can so that the referees, players and officials are brought to justice."

Police on Thursday made several arrests across Europe in connection with the alleged bribing of players and officials to fix the results of games.

UEFA confirmed more information about the matches concerned would be given at a later date, but revealed they are part of the UEFA list of 40 matches that have previously been quoted as being 'under suspicion'.

A UEFA statement read: "UEFA has been actively involved in the investigation and has given assistance via detailed information through its Betting Fraud Detection System.

"This detection system monitors all UEFA competitions and European national league first and second division matches for suspicious betting patterns. The information on a number of matches was passed to the German authorities upon their request."

UEFA general secretary Gianni Infantino said: "Firstly, I would like to thank the German authorities for their action and for the good collaboration.

"This case proves that it is possible for a state investigative authority to work closely together with a sports governing body when it comes to corruption or match fixing, and it is gratifying to see that the Betting Fraud Detection System endorsed by the UEFA president, Michel Platini, is already bearing fruit.

"We will continue our battle against any form of corruption in European football with a mission of zero tolerance.

"UEFA will be demanding the harshest of sanctions before the competent courts for any individuals, clubs or officials who are implicated in this malpractice, be it under state or sports jurisdiction."

Bochum prosecutors revealed the investigation had been under way since the start of the year.

The German Football Association (DFB) said in a statement UEFA and the Bochum prosecutors could count on their full support and that of the League Association.

DFB president Dr Theo Zwanziger said: "We are pleased that the state authorities investigate all suspicious circumstances with a high level of competence and seriousness.

"Because criminal acts are concerned, the Bochum public prosecutor is in charge of the operation. We are very thankful for their active work and they enjoy our full trust."

League Association president Dr Reinhard Rauball added: "We owe it to the fans that we do everything in our power to guarantee a clean competition.

"But first the presumption of innocence applies. But it is clear we cannot tolerate even a single game being manipulated."

The DFB ruled out the possibility of games being replayed if they were proved to have been manipulated.

German referee Robert Hoyzer was convicted of fraud in 2005 after admitting he had manipulated games.