A Belgian court has acquitted the Church of Scientology of charges of forming a criminal organisation, and dismissed demands that it should close its Belgian branch and European headquarters.

The church's Belgian branch, its European headquarters and a number of church members were accused by prosecutors of forming a criminal organisation over alleged fraud, unlawful medical practice, extortion and invasion of privacy.

They had called for it to be disbanded, along with prison terms for the members on trial.

However, presiding judge Yves Regimont dismissed all the charges against the church, which said it had been unfairly hounded for years by Belgian authorities.

"The entire proceedings are declared inadmissible for a serious and irremediable breach of the right to a fair trial," the judge said.

The judge criticised the investigators for what he said was prejudice, and prosecutors for being vague in their case against the religion.

"This was a religious case and nothing else," Pascal Vanderveeren, lawyer for the church, told reporters after the ruling.

"If you've said that you've said it all."

He denounced the case as careless and prejudiced aimed at "attacking Scientology and not those who are part of it".

"It's a relief," Scientology's spokesman in Belgium, Eric Roux, told reporters outside the court.

"When you have had 20 years of your life under a pressure that you know is unfair, where one attacks your beliefs and not something you have done, the day when the court says it officially, it's a big relief."

Twenty years of investigation

Marie Abadi, a former Scientology worshipper who has become a strong opponent, expected an appeal.

"We are evidently very disappointed. Either the facts are too old, or not precise enough. We are certain the prosecutor will appeal because things must budge," she said.

The Belgian trial began in October 2015 after nearly 20 years of investigations.

This included grouping together complaints from former members who sought to reclaim money from the church and the Brussels labour department, which said the scientologists had posted false job offers in the hope of finding new recruits.

Security was particularly tight for the verdict, with a heavy police presence and frisking of the public on entry to the courtroom, after demonstrators had threatened to disturb the sitting.

Scientology has fought a series of legal battles across the world to have itself recognised as a religion.

The church is championed by superstar members, such as Hollywood actors Tom Cruise and John Travolta, but is divisive, with critics saying it as a cult and a scam, while supporters say it offers much-needed spiritual support in a fast-changing world.

ABC/wires