BRASILIA (AFP) - Brazil's antitrust body announced a probe into alleged foreign exchange market rigging by 15 banks including Citigroup and HSBC, accused of colluding to form a secret cartel.

"There are strong indications of anticompetitive practises of price fixing" and other manipulations between the banks, the watchdog known as Cade said late Thursday.

The alleged cheating lasted from 2007 until at least 2013, authorities said.

"The evidence shows that (the banks) formed a cartel" fixing prices, coordinating trades, and impeding other operators involved in the Brazilian market, the watchdog said.

Brazilian investigators say the banks under scrutiny communicated online via the Bloomberg chat platform to organise what they themselves referred to as "The cartel" and "The mafia."

The other 13 banks named are: Banco Standard de Investimentos, Tokyo-Mitsubishi UFJ, Barclays, Credit Suisse, Deutsche Bank, JPMorgan Chase, Merrill Lynch, Morgan Stanley, Nomura, Royal Bank of Canada, Royal Bank of Scotland, Standard Chartered and UBS.

In addition to the institutions, the probe is targeting 30 individuals who were not identified.

Similar probes around the world, including in South Africa, South Korea, Europe and the United States have targeted much of the same group of banks.

In May, US and British regulators fined Barclays, JPMorgan Chase, Citicorp, Royal Bank of Scotland, UBS and Bank of America a total of nearly US$6 billion (S$8 billion) between them for rigging foreign exchange market and Libor interest rates.

No Brazilian banks were named in the investigation.