Voters are selecting 300 lawmakers who will serve in the General Assembly for the next four years. The election will also shape the next presidential election, which is just eight months away, The Chosun Ilbo reported.
Yonhap News Agency said exit polls show rival parties running extremely close, with public broadcaster KBS predicting the ruling Saenuri Party and the main opposition Democratic United Party will each win between 131 and 147 seats. Similar forecasts were offered by other media outlets.
The minor opposition Unified Progressive Party was projected to win as few as 10 and as many as 21 seats.
Turnout late in the day was estimated at 49.3 percent. Final turnout is expected to top 50 percent.