South Korean shares opened lower Thursday due to lingering worries over Britain's possible withdrawal from the European Union.

The benchmark Korea Composite Stock Price Index fell 6.28 points, or 0.32 percent, to 1,986.20 in the first 15 minutes of trading.

The outcome of the Brexit vote is scheduled to be officially announced at around 3 p.m. Friday (Korean time) after the referendum ends at 6 a.m. on the same day.

Two separate polls, conducted after the murder of a pro-EU lawmaker Jo Cox last week, showed the "Leave" camp was marginally ahead of the "Remain" camp. 

Weighing on the broader index, market bellwether Samsung Electronics Co. declined 0.21 percent, and the state-run Korea Electric Power Corp. slid 1.01 percent. No. 1 refiner SK Innovation Co. was down 1.37 percent.

Among gainers were top automaker Hyundai Motor Co., which advanced 0.36 percent. Leading chemical player LG Chem Ltd. Rose 0.39 percent. 

The local currency was trading at 1,151.10 won against the U.S. dollar, up 3.30 won from the previous session's close. (Yonhap)