The nation’s financial regulator on Thursday reprimanded Korean operations of three foreign banks for engaging in a cartel practice over prices of a currency swap.

The Financial Supervisory Service said the Seoul branches of French-based BNP Paribas S.A., Singapore-based DBS Bank Ltd., and Australia/New Zealand-based Australia New Zealand Banking Group Ltd. colluded.

To lower rates for a Korean company’s $10 million currency swap of foreign currency bonds.

All three ended up with 4.18 percent swap rates, lower than the 4.07-4.10 percent range that the Korean swap partner suggested.

The FSS fined the banks 50 million won ($45,000) each.

BNP Paribas, the largest bank in France, was the first among the three to be implicated, during the investigation in November and December 2012.

Besides a 50 million won fine, its the FSS punished five executives of the local branch and issued an institutional warning.

The other two, Seoul operations of DBS and ANZ, were caught after they were found involved with the French bank. The FSS launched a separate investigation between Dec. 17 and Dec. 18.

BNP Paribas’ local unit was also punished for conducting unlicensed brokerage services with financial vehicles worth 700 billion won.

The banking regulations stipulate that there should be a strict firewall between the (commercial or corporate) banking and the investment banking units unless there is regulatory approval.

“BNP Paribas was found to have operated an investment banking business in Seoul without regulators’ permission,” said an official.

By Chung Joo-won (joowonc@heraldcorp.com)