Three ex-Rabobank traders charged with manipulating Yen Libor

Three former traders at Dutch lender Rabobank were criminally charged on Monday with manipulating the Yen Libor benchmark interest rate, the U.S. Department of Justice said.

Two former Japanese Yen derivatives traders and a third trader responsible for setting the bank's Yen Libor rate were accused of submitting fraudulent rates in order to benefit their trading positions, the Justice Department said.

(Read more: Dutch Rabobank fined $1 billion over Libor scandal)

The exterior of the headquarters of Dutch co-operative bank Rabobank.
Lex Van Lieshout | AFP | Getty Images

In October, Rabobank paid $1 billion to resolve U.S. and European probes into rate-rigging allegations, making it the fifth bank punished in the scandal that has swept the industry.

A federal judge in New York signed a criminal complaint charging Paul Robson, a senior trader in London; Paul Thompson, who ran a trading desk in Singapore; and Tetsuya Motomura, a senior trader and supervisor on the bank's Tokyo desk, the department said. Charges included wire fraud and conspiracy to commit wire fraud, it said.

(Read more: Former UK traderHayes pleads 'not guilty' to Libor)

Robson, Thompson, and Motomura could not be immediately reached for comment.

The Libor rates that oil the wheels of global finance are an average rate at which a panel of banks say they could borrow money. The manipulation of related benchmarks has resulted in $3.7 billion in fines to date.

London InterBank Offered Rate (LIBOR): CNBC Explains

"The illegal manipulation of this cornerstone benchmark rate undermines the integrity of the markets; it harms those who are relying on what they expect to be an honest benchmark; and it has ripple effects that extend far beyond the trading at issue here," said Mythili Raman, who is acting head of the Justice Department's criminal division.

(Read more: European bank stocks could see 35% rally)

The Justice Department describes the three working with each other and other traders to move the rate between 2006 and 2011.

When one trader asks Robson in a September 2007 email for a higher Yen rate, Robson replies: "sure no prob ... I'll probably get a few phone calls but no worries mate ... there's bigger crooks in the market than us guys!"

At times Robson describes the skewed submission as "embarrassing," "ridiculously high" and "obscenely high," the Justice Department said.

U.S. criminal prosecutors have previously charged five other traders or brokers over similar conduct, but all remain overseas.

(Read more: Banks hit with $2.3billion rate-rigging fine)

The defendants could face up to 30 years in prison, but it is unclear if prosecutors will be able to bring them to the United States to face the charges.