The former banker was found guilty on Wednesday of breaching Swiss banking secrecy laws [Reuters]

Just hours after being found guilty of breaching Swiss bank privacy laws, Rudolf Elmer, a former banker, has been arrested over the leaking of details of rich and famous alleged tax evaders to the whistleblowing website WikiLeaks.

Elmer was taken into custody on Wednesday evening, having been found guilty by a Zürich court of sharing private client data and of threatening an employee at Julius Baer, his former firm, earlier in the day.

He was arrested on fresh charges of breaching secrecy laws.

"The state prosecutor's office is checking to see whether Rudolf Elmer has violated Swiss banking law by handing the CD over to Wikileaks," the Zürich cantonal (state) police and state prosecutor said in a joint statement.

At a news conference on Monday, Elmer handed data on hundreds of offshore bank accounts to Julian Assange, the WikiLeaks founder.

Prosecutors allege that he stole the information after being fired from his job.

Elmer previously helped to bring WikiLeaks to prominence three years ago when he handed over secret client information to the website.

'Murky oases'

At Wednesday's trial, Elmer admitted sending confidential bank data to tax authorities, but he denied charges of blackmail and a bomb threat against Julius Baer, as alleged by prosecutors.

He also denied taking payments in return for the secret data.

Elmer said he wanted to expose widespread tax evasion by rich businesspeople and politicians when he sent confidential banking files to tax authorities, media and later to WikiLeaks.

"I am a critic of the system and want to tell society what happens in these murky oases," Elmer, who ran the Cayman Islands branch of the Swiss bank, told a news conference before the verdict.

Judge Sebastian Aeppli rejected prosecution demands to give Elmer an eight-month prison sentence for breaching the bank secrecy laws and instead the court sentenced him to a fine of 7,200 Swiss francs ($7,505), suspended for two years

The trial drew broad media attention and about a dozen protesters gathered in front of the court building.

"We think those who expose the distasteful side of Swiss finance need our support," Walter Angst, one of the protesters, said.

Several Swiss banks including UBS, AG and Credit Suisse Group have suffered embarrassing data leaks in recent years, some at the hands of disgruntled employees.