* Twenty players treated as suspects
* Police name 17 matches which could have been manipulated (Updates with players questioned, matches under suspicion)
Nov 28 (Reuters) - Twenty current and former footballers in the Austrian league are being treated as suspects over match-fixing and up to 17 first and second division matches could have been manipulated in the last seven years, criminal investigators said Thursday.
The revelations came one day after the arrest of defender Dominique Taboga, who was released by first division SV Groedig two weeks ago over match-fixing allegations.
Altogether, six people are currently in custody in connection with the case, including former Austria international forward Sanel Kuljic and two Albanian citizens, investigators and state prosecutors told a news conference in Salzburg.
Investigators said that the 17 matches under suspicion included nine in the Bundesliga, the top flight of Austrian football, of which three were played this season involving Groedig.
These were Groedig's 3-0 defeat by local rivals Salzburg in October, their 1-1 draw at home to Wolfsberger earlier this month and their 2-2 draw against Rapid Vienna, also this month.
The remaining eight games were all in the Erste Liga, the second tier of Austrian football. Nine of the 17 matches involved former Bundesliga club Kapfenberger, relegated at the end of the 2011-12 season.
Federal criminal investigator Andreas Holzer told the news conference that a list of 30 players had been found in Operation Rinas as police carried out house searches in Vienna, Salzburg, and the provinces of Carinthia and Lower Austria.
"Twenty of them have already been questioned and are being treated as suspects," he said. "As you can imagine, the investigations are very complicated, it's an international investigation which is difficult to carry out."
He said that in some cases, bets may have been placed on incidents such as penalties or corners rather than the result of the match itself.
Taboga was arrested on Wednesday in the town of Kaernten. The 31-year-old left Groedig by mutual consent on Nov. 14 after the club said he had admitted trying to persuade four team mates to manipulate matches.
The club said the other players declined to get involved and the match-fixing never took place.
Kuljic was arrested along with two men over allegations that they tried to blackmail Taboga in the case. Prosecutors said that police caught them collecting money from Taboga at a shopping centre car park near Salzburg earlier this month.
Kuljic, who retired as a player last year, played for Austria 20 times between 2005 and 2007 but failed to make the cut for the Euro 2008 squad. He was joint topscorer in the Austrian Bundesliga in 2005/06 for SV Ried with 15 goals.
The Bundesliga and Austrian Football Federation (OeFB) said in a joint statement that they supported the investigations.
"As soon as we have results, we will start to take action. It should be made unmistakably clear that potential offenses will be punished with all severity," said the statement.
"This procedure is being carried out in coordination with the Federal Criminal Police Office, with whom there is an excellent cooperation."
Groedig, based in a small town near Salzburg and the German border, were promoted last season and are playing in the top flight for the first time. (Writing by Brian Homewood in Berne; Editing by Clare Fallon and Justin Palmer)