* Coal company takeover a big Czech privatisation scandal
* Swiss government freezes $700 million in case
* Czech authorities slow to cooperate, but bring charges
* Defendants say they are innocent
By Martin de Sa'Pinto and Jan Lopatka
BELLINZONA, Switzerland/PRAGUE, May 13 (Reuters) - One of the biggest scandals dating back to central Europe's post-communist privatisation boom came to trial on Monday in a Swiss court, years after alleged money laundering that prompted the freezing of around half a billion euros.
Swiss prosecutors say the six defendants - five Czechs and a Belgian - conspired to gain control of major Czech miner Mostecka Uhelna Spolecnost (MUS), now called Czech Coal, between 1997 and 2003. The defendants say they did nothing illegal.
Repeated Czech investigations into the case involving several prominent Czech investors came to nothing, upsetting Swiss authorities and prompting critics to suggest impotence or bias on the part of the Czech authorities.
But following the appointment of new prosecutors, widely seen as more aggressive in their pursuit of uncovering graft, Czech authorities also charged the managers last year.
Swiss prosecutors say the defendants used MUS's own cash to build up a half share in the company.
They add that they then secured an artificially low price from the government for the rest in a privatisation deal through a group called Appian, and ran a series of related transactions through a web of accounts.
"The accused are charged with organising, between 1997 and 2003, the wholesale diversion of the financial assets of ... Mostecka Uhelna Spolecnost (MUS)... with the principal aim of taking control of the company's funds and buying its shares on their own behalf," said the prosecution file, released at the start of the trial in the southern Swiss town of Bellinzona.
THREE DEFENDANTS ATTEND
The Swiss government has frozen 660 million Swiss francs ($701.57 million) related to the case, and legal sources said it was one of the authorities' most complex money-laundering investigations to date.
The case comes as Switzerland seeks to clean up its image as a haven for ill-gotten gains.
The defendants, three of whom attended the opening of the trial, all say they did nothing illegal and the Swiss transactions were of a purely commercial nature. They have since sold the firm, but some remain investors in Czech industry.
"All the defendants feel they are innocent on all points of the charges," Karolina Zelenkova, a lawyer representing the Czech defendants, was quoted as saying by local media.
The other three accused, including the Belgian, were summoned by the court to attend at a later date.
A lawyer for the Belgian defendant, former International Monetary Fund official Jacques de Groote, did not immediately respond to requests for comment.
As part of their case, Swiss prosecutors say MUS and Portoinvest, based in Vaduz, Liechtenstein and controlled by one of the accused Jiri Divis, used transactions via accounts at UBS in Zurich and Credit Suisse in Fribourg to raise Portoinvest capital by $140 million.
The banks declined to comment, citing confidentiality rules, while Divis said at the court that he had no comment to make.
Former Czech Prime Minister Stanislav Gross suspended his own membership of the Social Democrats in 2011 pending the investigation, but he was not accused or named in the case.
Gross was a senior party figure when the privatisation of the remaning state stake went through but was not yet in the cabinet, which was headed by current President Milos Zeman.
($1 = 0.9408 Swiss francs) ($1 = 19.6720 Czech crowns) (Editing by Mike Collett-White)