US prosecutors have filed an indictment against the operators of digital currency exchange Liberty Reserve, accusing the Costa Rica-based company of helping criminals around the world launder more than $6bn.

The money came from illicit funds linked to everything from child pornography to software for hacking into banks.

The indictment unsealed on Tuesday said Liberty Reserve had more than a million users worldwide, including at least 200,000 in the US, and virtually all of its business was related to suspected criminal activity.

Preet Bharara, a US lawyer, called the case perhaps "the largest international money-laundering case ever brought by the United States".

"Liberty Reserve has emerged as one of the principal means by which cyber-criminals around the world distribute, store and launder the proceeds of their illegal activity," according to the indictment filed in the US District Court for the Southern District of New York.

Officials said authorities in Spain, Costa Rica and New York arrested five people on Friday, including the company's founder, Arthur Budovsky, and seized bank accounts and internet domains associated with Liberty Reserve.

The indictment detailed a system of payments that allowed users to open accounts under false names such as "Russia Hackers" and "Hacker Account".

The use of digital currency has expanded over the past decade, attracting users ranging from video gamers looking for ways to buy and sell virtual goods to those who lack faith in the traditional banking system.

Touted by some investors as the future of money, these virtual currencies have gained the attention of US regulators looking to bring them under anti-money laundering rules.

The US treasury said on Tuesday it named Liberty Reserve under the USA Patriot Act as "specifically designed and frequently used to facilitate money laundering in cyber space".

Source: Reuters