By Christine Kim

SEOUL (Reuters) - South Korea said on Wednesday it will react firmly to severe financial market volatility if needed after Republican Donald Trump stunned the world by winning the race for U.S. president House, sending global markets plunging.

The government and central bank said they plan to boost monitoring of markets around the clock.

"We plan to consider ways to provide market liquidity through a number of methods, including issuing foreign currency bonds, flexible use of macroprudential measures, and foreign currency funding for the private sector," Finance Minister Yoo Il-ho said during a meeting to discuss the election.

South Korean stocks plunged to their lowest level in four months while the won notched its biggest daily fall since mid-September as market investors braced for a shock victory by Trump.

Yoo urged markets to remain calm, while adding downside risks to the global economy have increased as a result of the vote.

A Trump administration is expected to heighten trade protectionism, which would hurt major exporters in South Korea like Samsung Electronics Co Ltd and Hyundai Motor Co.

Shares in both companies slumped on Wednesday, along with most others in South Korea's main bourse.

But Yoo noted that Trump's campaign pledges may not end up as actual policy.

In a separate statement, South Korea's trade ministry said it will consider ways to respond to any possible trade policy changes in the U.S. that may include tightened restrictions for imports there.

(Additional reporting by Cynthia Kim; Editing by Kim Coghill)