* KOSPI index down, foreign investors sell * Korean won falls versus U.S. dollar * South Korea bond yields slip SEOUL, May 15 (Reuters) - Round-up of South Korean financial markets: ** South Korea's KOSPI stock index weakened on Tuesday, following a tepid Wall Street performance overnight, while the greenback's broad strength weighed on the Korean won in onshore trading, and bond yields fell. ** At 01:34 GMT, the KOSPI was down 5.60 points or 0.23 percent at 2,470.51, with the index's kingpin Samsung Electronics declining 1 percent, its third session of losses, while LG Electronics dropped 2 percent. ** The won was quoted at 1,070.6 per dollar on the onshore settlement platform , 0.24 percent weaker than its previous close at 1,068. ** In offshore trading, the won was quoted at 1,071 per U.S. dollar, down 0.08 percent from the previous day, while in one-year non-deliverable forwards it was being transacted at 1,054.25 per dollar. ** MSCI's broadest index of Asia-Pacific shares outside Japan was down 0.36 percent, after U.S. stocks ended the previous session with mild gains. Japanese stocks rose 0.11 percent. ** The KOSPI is up around 0.3 percent so far this year, and has risen 1.63 percent in the previous 30 days. ** The current price-to-earnings ratio is 12.10, the dividend yield is 1.28 percent and the market capitalisation is 1,242.04 trillion won. ** The trading volume during the session on the KOSPI index was 307,297,000 shares and, of the total traded issues of 884, the number of advancing shares was 373. ** Foreigners were net sellers of 51,576 million won worth of shares. ** The U.S dollar has risen 0.43 percent against the won this year. The won's high for the year is 1,053.55 per dollar on April 2 and the low is 1,098.4 on Feb. 6. ** In money and debt markets, June futures on three-year treasury bonds rose 0.02 points to 107.49. ** The Korean 3-month Certificate of Deposit benchmark rate was quoted at 1.65 percent compared with a previous close of 1.65 percent, while the benchmark 3-year Korean treasury bond yielded 2.301 percent, lower than the previous day's 2.31 percent. (Reporting by Cynthia Kim; Editing by Biju Dwarakanath)