KOSPI falls, foreigners net buyers Korean won weakens against U.S. dollar South Korea benchmark bond yield rises SEOUL, Jan 5 (Reuters) - Round-up of South Korean financial markets: ** South Korean shares dropped more than 1% on Wednesday, as tech heavyweights declined and institutional investors extended their selloff in equities that went ex-dividend. The Korean won hit a 12-week low, while the benchmark bond yield rose. ** By 0159 GMT, the benchmark KOSPI (.KS11) fell 38.86 points, or 1.30%, to 2,950.38, set for the sharpest daily fall since Dec. 20. ** Among heavyweights, chip giants Samsung Electronics (005930.KS) and SK Hynix (000660.KS) fell 2.16% and 4.67%, respectively, while platform company Naver (035420.KS) also slipped 2.33%. ** Institutional investors were net sellers of 655.9 billion won ($547.12 million) worth of shares on the main board, according to the Korea Exchange data, extending the selling spree to a fifth straight session. ** Foreigners, however, were net buyers of 56.2 billion won worth of shares. ** Meanwhile, analysts" estimates showed on Wednesday that Samsung Electronics is likely to post a record fourth-quarter profit, thanks to solid demand for server memory chips and higher margins in contract manufacturing. read more ** "South Korea"s software sector tracked overnight losses in Nasdaq due to weak tech shares and higher U.S. yields," said Mirae Asset Securities" analyst Seo Sang-young. ** The won was quoted at 1,197.8 per dollar on the onshore settlement platform , down 0.31%. ** In offshore trading, the won was quoted at 1,198.8 per dollar, down 0.1%, while in non-deliverable forward trading, its one-month contract was quoted at 1,199.6. ** In money and debt markets, March futures on three-year treasury bonds fell 0.03 points to 108.73. ** The most liquid 3-year Korean treasury bond yield rose by 2.8 basis points to 1.893%, while the benchmark 10-year yield rose by 4.3 basis points to 2.357%. ($1 = 1,198.8300 won)