KIA, the nation's sovereign-wealth fund, bought the preferred securities for $3 billion last year to boost the bank's capital during the financial crisis.
It converted them into common shares in order to make the sale.
News of the deal saw shares in Citigroup fall to $4 in European trading today, a 1.5 per cent drop on its price at the end of trading in New York last Friday.
The most recent drop means shares in the bank have fallen by 47 per cent over the course of the year, reports Bloomberg.
Citigroup appears no nearer to ridding itself of its obligations to the government, with officials saying the Treasury will not sell off its 34 per cent stake in the company until the bank can agree a plan with regulators to pay off all of its bailout debts.
It is desperate for the government to sell its assets as it believes investors are currently shying away from purchases as an eventual government sell-off will drive down share prices.
By Tony Aynsley