The benchmark Korea Composite Stock Price Index rose 7.88 points, or 0.38 percent, to 2,085.82 in the first 15 minutes of trading.
Investors welcomed a severance deal between Britain and the EU that could wrap up more than three years of uncertainty after Britain decided to leave the EU.
In Seoul, large caps were mixed.
Market kingpin Samsung Electronics added 0.2 percent, top automaker Hyundai Motor rose 1.22 percent and top steelmaker POSCO fell 0.22 percent.
The Korean won was trading at 1,179.70 won against the US dollar, up 7.3 won from the previous session's close. (Yonhap)