South Korean stocks fell to the lowest in 15 months Thursday on rising worry about the global trade conflict, caused by the U.S. protectionist moves.

The benchmark Korea Composite Stock Price Index (KOSPI) shrank 18.11 points, or 0.80 percent, to settle at 2,240.80. Trading volume stood at 309.36 million shares worth 5.93 trillion won (5.25 billion U.S. dollars).

Concerns about trade war deepened in the stock market as U.S. President Donald Trump tweeted last week that he had authorized the doubling of import tariffs on steel and aluminum products from Turkey.

The White House said overnight that the United States will not lift sanctions on Turkish steel and aluminum products even if detained U.S. pastor Andrew Brunson is released.

In response, Turkish President Recep Tayyip Erdogan signed a decree to raise tariffs on some U.S. imports including cars, alcohol and tobacco.

U.S. stocks lost ground overnight on rising worry about trade conflict, leading to the KOSPI's fall to the lowest since May 2, 2017.

Foreigners remained net sellers in the local stock market for the fifth trading day. Retail investors were net buyers, but local financial institutions sold stocks.

Market bellwether Samsung Electronics declined 2 percent, and memory chip giant SK Hynix retreated 1.6 percent. Samsung Biologics, the biosimilar-making unit of Samsung Group, the country's biggest family-run conglomerate, slumped 3.5 percent.

The biggest steelmaker POSCO dipped 2.6 percent, but the No.1 automaker Hyundai Motor advanced 2.9 percent. Top auto parts manufacturer Hyundai Mobis added 1.1 percent.

South Korea's currency finished at 1,130.1 won against the greenback, down 2.2 won from the previous close. The local currency's depreciation came as dealers sold the currency to win safe-haven assets such as the dollar funds.