Foreigners sold a net 2 trillion won (1.2 billion pounds) out of local bonds and stocks last month, the Financial Supervisory Service (FSS) said in a statement, the biggest outflow since February last year.
The bulk of the outflows last month, a net 1.9 trillion won, were in stocks as offshore investors bailed out of riskier assets amid a rout in oil prices and broad concerns over global growth.
Foreigners bought a net 2.0 trillion won worth of Seoul stocks in November.
South Korean stock prices have been on a steady decline since late July last year, with sentiment also depressed by slowing growth in China and a sickly euro zone economy.
Investors in the U.S. were the biggest sellers, offloading a net 0.7 trillion won worth of stocks, followed by those in the U.K. and Saudi Arabia with net sales of 0.6 trillion won and 0.3 trillion won respectively, according to the FSS data.
The main bourse was trading down more than 9 percent shortly after markets opened on Thursday compared to its peak reached in July 2014.
The FSS data also showed foreign investors lowered their holdings of South Korean bonds for the first time in four months in December, though only by a modest 0.1 trillion won.
In November, offshore investors boosted their holdings of won-denominated bonds by 0.5 trillion won.
Malaysia withdrew the most money, taking out 0.8 trillion won from their investment in local bonds, FSS said, while China placed the most money in South Korean bonds for a second straight month by increasing their holdings by 0.6 trillion won.
The FSS does not provide comments or explanations for the monthly changes in offshore investments in stocks or bonds.
(Reporting by Christine Kim; Editing by Shri Navaratnam)
