The benchmark Korea Composite Stock Price Index gained 6.74 points, or 0.29 percent, to 2,336.39 in the first 15 minutes of trading.
On Sunday, Pyongyang claimed it successfully conducted a test of a hydrogen bomb that can be loaded on an intercontinental ballistic missile.
Tech shares led the recovery, with top cap Samsung Electronics advancing 0.13 percent and chipmaker SK hynix adding 0.59 percent.
Home appliance maker LG Electronics moved up 3.26 percent.
Leading carmaker Hyundai Motor rose 0.71 percent, and its smaller affiliate Kia Motors increased 0.57 percent. Auto parts maker Hyundai Mobis gained 1.26 percent.
The local currency was trading at 1,129.90 won against the US dollar, up 3.10 won from the previous session's close. (Yonhap)