With U.S. President Donald Trump warning of a closure of the Strait of Hormuz and raising tensions, the KOSPI closed at the 5,800 level. Retail investors supported the index even as foreigners and institutions sold.

The KOSPI ended down 50.25 points, or 0.86 percent, at 5,808.62. It opened down 121.59 points, or 2.08 percent, at 5,737.28 and slid to as low as 5,730.23 before paring losses.

By investor type, individuals were net buyers of 748.2 billion won. Foreigners and institutions were net sellers of 449.7 billion won and 706.5 billion won, respectively. Foreigners returned to net selling for the first time in 5 sessions.

Top market-cap stocks were mixed. Samsung Electronics closed down 2.43 percent at 201,000 won, while SK Hynix ended up 1.27 percent at 1,040,000 won. Hyundai Motor and LG Energy Solution fell 2.25 percent and 2.55 percent, respectively.

Hanwha Aerospace rose 1.53 percent and SK Square gained 2.11 percent. Samsung Biologics fell 1.34 percent, Doosan Enerbility lost 0.90 percent and KB Financial Group slipped 1.07 percent.

The Kosdaq ended up 6.21 points, or 0.57 percent, at 1,099.84.

The won-dollar exchange rate was 1,489.20 won per dollar, up 3.70 won from the previous session.