The Monetary Authority of Singapore (MAS) found that 133 traders had tried to influence the rates in an echo of the 2012 US/UK Libor rigging scandal.
Some of the cases have been referred to the police, and the city-state’s Attorney General Chambers.
UBS, Royal Bank of Scotland and ING have been told to set aside funds of over S$1bn (£500m; $800m) each.
Another 16 banks have also been ordered to set aside lesser amounts, including Barclays, Deutsche Bank, JP Morgan and HSBC, as statutory reserves at the MAS.
The central bank ordered a review into the way banks located in the country set benchmark rates for borrowing and foreign exchange transactions.
The Association of Banks in Singapore and the Singapore Foreign Exchange Markets Committee, which carried out the review, have recommended scrapping publication of the Singapore Interbank Offered Rate (Sibor) – a benchmark for borrowing costs.