MUNICH - A man dubbed the "Swiss Gigolo" was sentenced to six years in prison Monday for defrauding the country's richest woman of $9 million US and attempting to blackmail her for millions more.

Helg Sgarbi admitted to the Munich court that he threatened to release secretly recorded videotapes of trysts with BMW heiress Susanne Klatten, 46, who was married, unless she gave him millions to keep quiet.

The 44-year-old also admitted convincing Klatten to give him $9 million by saying it was to treat a girl left paraplegic after he hit her with his car.

The Munich state court found Sgarbi guilty of fraud and attempted blackmail of Klatten.

He was found guilty of further counts of fraud and attempted blackmail for taking $3 million from three other women -- identified only by the initials H., R., and S. -- who were found as police investigated the Klatten case.

Prosecutor Thomas Steinkraus-Koch praised Klatten for her bravery.

"The only victim who came to us and gave a witness statement is Mrs. Klatten. We had to find the others, with great difficulty," Steinkraus-Koch said.

The four were the latest in a string of women conned by Sgarbi, a lawyer who spoke six languages, worked as a banker at Credit Suisse until the mid-1990s, and served as a reserve officer in the Swiss army, according to prosecutors.

Germany's Stern magazine reported that one victim, a countess 50-years older than Sgarbi, turned him in to Swiss police in 2001 but then had the charges dropped after he returned $17 million to her.

Steinkraus-Koch confirmed a case had been dropped in Switzerland, and said Sgarbi had been sentenced to six months probation in a similar case, also in Switzerland.

Klatten did not attend the trial and her lawyer made no statement to the court. Her spokesman was not immediately available for comment.

Her husband, Jan Klatten, has also made no comment but according to details released in court the couple remain married and have been working through their difficulties.

Sgarbi told the court he laid the groundwork for his fraud against Susanne Klatten when he first met her at a spa near Innsbruck, Austria, in July 2007.

He showed up a month later at her vacation home in the south of France and their affair began in earnest. Then he told Klatten that he was involved in a car accident in the United States that left a girl paralyzed, and convinced Klatten to give him money for the girl's treatment.

According to her police statement, Klatten eventually met Sgarbi in a parking garage to hand over cash worth $9 million in a cardboard box.

Sgarbi then demanded that Klatten leave her family and invest $367 million in a trust for him, according to the indictment. When she refused, he threatened to release secretly filmed videos of their affair.

Sgarbi demanded $62 million not to tell her family, the heads of her companies and the media. He lowered the demand to $18 million but in January 2008 Klatten went to the police. Sgarbi was arrested shortly afterward in Austria's Tyrolean Alps and has been held in detention since.

Another man arrested with him, identified only as an Italian named Ernano B., is wanted by German authorities as an accomplice. He was sent to Italy, where he was sought on charges related to organized crime. A request for his extradition has been refused.

Klatten is the daughter of the late BMW magnate Herbert Quandt and holds a 46 per cent stake in the company along with her mother and brother. She also owns an 88 per cent share of the chemical company Altana.

Forbes magazine listed her as the 68th richest person in the world last year, with a personal fortune of around $9.6 billion. The story has attracted vast media attention in Germany, where the Quandt family is regarded as quasi-royalty.

"I deeply regret what has happened and apologize to the aggrieved ladies in this public hearing," Sgarbi told the court. Sgarbi's lawyer, Egon Gries, said his client would not answer any questions about where the money had gone or whether anyone had helped him.

Sgarbi had faced a possible 10-year sentence, but presiding Judge Gilbert Wolf said he decided on six years because Sgarbi's confession had spared his victims from having to testify.