* KOSPI falls, foreigners net sellers

* Korean won weakens against dollar

* South Korea benchmark bond yield falls

SEOUL, June 21 (Reuters) - Round-up of South Korean financial markets:

** South Korean shares extended losses on Wednesday for a third straight session as cautious investors remained on the sidelines ahead of U.S. Federal Reserve Chair Jerome Powell's congressional testimony.

** The Korean won weakened nearly 1%, while the benchmark bond yield fell.

** The benchmark KOSPI was down 11.58 points, or 0.44%, to 2,593.33, as of 0211 GMT.

** "The benchmark index is also undergoing a correction period from its recent rally, with investors booking profits amid a wait-and-see mood," said Lee Jong-bin, analyst at Meritz Securities.

** Powell is scheduled to give a testimony before the U.S. House of Representatives' Financial Affairs Committee later in the day.

** South Korea's exports for the first 20 days of June rose 5.3% from the same period a year earlier, marking the first increase in 10 months.

** Shares of Korea Electric Power (KEPCO) fell 0.16% after South Korea kept electricity rates for the July-September quarter unchanged after two hikes in the first half of the year.

** Chipmaker Samsung Electronics fell 0.84%, but peer SK Hynix gained 0.34%, while battery maker LG Energy Solution lost 0.53%.

** Among other index heavyweights, Hyundai Motor and its sister automaker Kia Corp jumped 1.31% and 1.71%, respectively. Search engine Naver dropped 3.38%, while instant messenger Kakao traded down 1.74%.

** Of the total 930 issues traded, 252 shares rose.

** Foreigners were net sellers of shares worth 229.1 billion won ($177.44 million).

** The won was quoted at 1,292.5 per dollar on the onshore settlement platform, nearly 1% lower than its previous close.

** In money and debt markets, September futures on three-year treasury bonds rose 0.08 point to 104.08.

** The most liquid three-year Korean treasury bond yield fell by 0.2 basis point to 3.558%, while the benchmark 10-year yield dropped 2.4 basis points to 3.617%.

($1 = 1,291.1700 won) (Reporting by Jihoon Lee; Editing by Sherry Jacob-Phillips)