* KOSPI falls, foreigners net sellers

* Korean won weakens against U.S. dollar

* South Korea benchmark bond yield rises

* For the midday report, please click

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

** South Korean shares fell on Monday as worries about continued fighting in Ukraine overshadowed hopes that peace would be brokered in the conflict. The Korean won weakened, while the benchmark bond yield rose.

** The benchmark KOSPI closed down 20.97 points, or 0.77%, at 2,686.05. It gained as much as 0.40% earlier in the session to its highest level since March 4.

** Leading the declines, chip giants Samsung Electronics and SK Hynix fell 1.13% and 1.61%, respectively, while battery maker LG Energy Solution rose 1.05%.

** Ukraine on Monday rejected Russian calls to surrender the port city of Mariupol as they continued fierce fighting, despite attempts at peace talks between Russia and Ukraine.

** Investors are also eyeing a series of speeches by Federal Reserve policymakers this week, starting with remarks by Chair Jerome Powell later on Monday.

** At home, data on Monday showed South Korea's exports for the first 20 days of March jumped 10.1% from the same period a year earlier, while imports soared 18.9%, bringing the trade balance to a $2.08 billion deficit.

** Meanwhile, the country has reached a deal to buy 10 million doses of the country's first experimental coronavirus vaccine, developed by SK Bioscience Co Ltd.

** Foreigners were net sellers of 485.6 billion won ($399.58 million) worth of shares on the main board.

** The won ended at 1,216.3 per dollar on the onshore settlement platform, 0.72% lower than its previous close.

** In offshore trading, the won was quoted at 1,215.3, while in non-deliverable forward trading its one-month contract was quoted at 1,215.5.

** In money and debt markets, June futures on three-year treasury bonds fell 0.13 point to 107.43.

** The most liquid 3-year Korean treasury bond yield rose by 3.7 basis points to 2.268%. ($1 = 1,215.2900 won) (Reporting by Joori Roh)