Zurich - FIFA president Joseph Blatter called Monday for professional referees as a measure to protect football from the threat of match-fixing.

Blatter told a congress of football's world governing body in Zurich on sport betting that there appeared to "no limits" on what people were prepared to bet.

In reference to a recent match-fixing scandal in Germany which led to the jailing of a former referee, Blatter said there were still no professional referees in the Bundesliga.

"Nobody can say that the money is not there. We have to protect those who could be or already are the targets of such methods," he said.

Blatter, who has long called for the introduction of professional referees, rejected speculation that any matches at the 2006 World Cup in Germany could have been the target of match-fixers.

FIFA has introduced an early warning system for monitoring sports betting, which was first tested ahead of the 2006 World Cup.

Wolfgang Feldner, head of strategy for Early Warning System GmbH, the company founded to undertake the monitoring work, estimated 350 billion dollars (275 billion euros) a year gross was being placed on sport betting.

The organization, which is cooperating with international bookmakers, also monitored the Olympic Games in Beijing and is looking at qualification matches for the 2010 World Cup.

He said there were "many possibilities to remain undiscovered" in attempts at match-fixing, especially as bets are placed these days on all sorts of possibilities and not just the result of a match.

UEFA, football's governing body in Europe, is also looking at the possibility of corruption in European football.

It has set up an investigative unit which is looking at 10 UEFA Cup qualifiers and Intertoto Cup matches this summer, with doubts about 15 others from last season. (dpa)