The incident marks the latest crackdown by Japanese authorities over alleged attempts to manipulate prices in the JGB futures market.

The SESC said an employee of UK-based Citigroup Global Markets Limited made buy and sell orders for 10-year JGB futures without the intention to execute. The SESC recommended a penalty of 133 million yen.

Citigroup said it takes the recommendation seriously.

"Citi will place the utmost priority on further enhancing governance and internal control to comply with the financial regulations and directives," it said in a statement.

The SESC does not itself issue fines, which are ultimately handed down by the Financial Services Agency regulator.

In July the regulator slapped a fine of 218 million yen on a joint venture of Mitsubishi UFJ Financial Group and Morgan Stanley for trying to manipulate bond future prices.

(Reporting by Takahiko Wada; Writing by Junko Fujita; Editing by David Dolan and Kim Coghill)