South Africa's competition watchdog has recommended fines against banks including Citigroup, Nomura and Standard Bank equal to 10 percent of their annual revenues for rigging the rand currency, it said on Wednesday.
The Competition Commission said it had concluded an investigation into whether banks colluded by using an instant messaging chat room called "ZAR Domination", to coordinate their trading activities when giving quotes to customers who buy or sell currencies.
ZAR is the code for the South African rand used in financial markets.
The Commission did not say if the fines should relate to the global revenues of the banks in question or just their South African business.
Fictitious bids and offers
The probe found that from at least 2007, traders at these banks had an agreement to collude on prices for bids, offers and bid-offer spreads for spot trades involving the rand and the US dollar, the Commission said.
"They also created fictitious bids and offers, distorting demand and supply in order to achieve their profit motives," the Commission said in a statement.
The Commission launched the investigation in April 2015, joining a global clampdown on price-rigging in currency markets that has led to dozens of traders fired and big banks fined around $10 bn in total.
The Commission, which investigates anti-trust practices, said it had referred the case to the Competition Tribunal for prosecution.
Other banks named in the case are Investec, JP Morgan, BNP Paribas, Credit Suisse Group , Commerzbank AG , Standard New York Securities Inc, Macquarie Bank , Bank of America Merrill Lynch, ANZ Banking Group Ltd, Standard Chartered Plc and Barclays Africa, part of the Barclays Plc .