* KOSPI falls, foreigners net sellers

* Korean won weakens against U.S. dollar

* South Korea benchmark bond yield falls

* For the midday report, please click

SEOUL, Sept 9 (Reuters) - Round-up of South Korean financial markets:

** South Korean shares closed lower on Thursday to mark their sharpest fall in three weeks as platform tech companies like Kakao and Naver dropped on concerns of a regulatory crackdown.

** The won weakened and the benchmark bond yield fell.

** The benchmark KOSPI ended 48.29 points, or 1.53%, lower at 3,114.70.

** Among the heavyweights, technology giant Samsung Electronics fell 1.31% and peer SK Hynix dropped 2.83%. LG Chem shed 1.06% and Naver declined 2.56%.

** Kakao dropped 7.22% amid fresh discussions by ruling party members of new regulation against platforms.

** Investor sentiment was weakening as many are expecting fresh regulations on internet platform companies, while concerns about slowing U.S. economy also weighed, Mirae Asset Securities' analyst Kim Seok-hwan said.

** Foreigners were net sellers of 315.9 billion won ($270.11 million) worth of shares on the main board.

** The won was quoted at 1,169.2 per dollar on the onshore settlement platform, down 0.21%.

** In offshore trading, the won was quoted at 1,169.2 per dollar, down 0.2%, while in non-deliverable forward trading, its one-month contract was quoted at 1,169.7.

** The KOSPI has risen 8.40% so far this year, but lost 2.2% in the previous 30 trading sessions.

** The trading volume was 910.45 million shares. Of the total traded issues of 921, the number of advancing shares was 212.

** The won has lost 7.1% against the dollar so far this year.

** In money and debt markets, September futures on three-year treasury bonds fell 0.06 point to 110.20.

** The most liquid 3-year Korean treasury bond yield rose by 0.5 basis point to 1.498%, while the benchmark 10-year yield fell by 2.1 basis points to 1.998%. ($1 = 1,169.5100 won) (Reporting by Cynthia Kim, additional reporting by Jihoon Lee; editing by Uttaresh.V)