Image caption Steve Cohen, SAC Capital's founder, was not indicted

US authorities have launched criminal charges against the Wall Street hedge fund SAC Capital.

The fund is being charged with four counts of securities fraud and one count of wire fraud, after seven-year long investigation.

Prosecutors said the fund was involved in "systematic insider trading" that allowed it to make hundreds of millions of dollars in illegal profits.

SAC Capital refutes the accusation and says it will operate as normal.

It said in a statement it had "never encouraged, promoted or tolerated insider trading", adding that it took its compliance and management obligations seriously.

The hedge fund was indicted but not its founder, Steven Cohen.

'Suspicious information'

At its peak, the fund managed more than $15bn of assets for its clients.

Prosecutors said the alleged crimes date back to 1999 and continued until at least 2010.

They allege that SAC obtained inside information on publicly traded companies, and traded on that information to boost returns and fees.

Image caption SAC Capital had over $15bn of assets under management at its peak

"[SAC's] relentless pursuit of an information 'edge' fostered a business culture within SAC in which there was no meaningful commitment to ensure that such 'edge' came from legitimate research and not inside information," court filings said.

The criminal charges come just a week after the Securities and Exchange Commission (SEC) filed civil charges against SAC's billionaire founder and operator Steve Cohen, accusing him of failing to prevent insider trading at the firm.

The SEC alleges that Mr Cohen received "highly suspicious information" that should have caused him to "take prompt action to determine whether employees under his supervision were engaged in unlawful conduct".

Responding to those civil charges last week, an SAC spokesman said the allegations had "no merit" and that Steve Cohen "acted appropriately at all times".

Mr Cohen is one of the highest profile hedge fund managers on Wall Street, and one of the wealthiest, earning hundreds of millions of dollars a year.

He is reportedly worth an estimated $8bn.

The new criminal charges cap one of the biggest insider trading investigations in Wall Street history.

Investigators have also already charged four employees of the hedge fund with insider trading, and two have pleaded guilty.