(Updates to mid-morning)
* KOSPI aims for 7th consecutive winning session
* NH Investment & Securities jump on merger hopes
* Institutional investors again are net buyers
SEOUL, Dec 26 (Reuters) - Seoul shares inched to their highest level in more than three-weeks on Thursday morning, as the global economic outlook brightened, though post-Christmas holiday volume was light.
The Korea Composite Stock Price Index (KOSPI) was up 0.3 percent at 2,007.46 points at 0145 GMT after touching 2,008.15, its highest since Dec. 3.
The KOSPI has risen the past six sessions. Dec. 30 is the last trading day for local markets this year.
"The global economic outlook is improving and local stocks have cheapened enough for investors to buy them up heading into new year," said Choi Kwang-hyeok, an analyst at E-Trade Securities.
On Tuesday, s batch of U.S. economic indicators surged, pointing to sustained strength in the world's largest economy.
China's short-term money market rates extended their fall from six-month peaks on Wednesday, easing concerns about liquidity conditions for South Korea's largest export market.
However, the weakening yen against won remained an issue for exporters such as Hyundai Motor Co, which slipped 0.2 percent.
Naver Corp fell 1.2 percent and SK Hynix Inc dipped 0.8 percent on profit-taking.
NH Investment & Securities Co Ltd, the brokerage unit of NongHyup Financial Group Inc, leaped 6.5 percent, after the parent was named Tuesday as preferred bidder to buy controlling stakes in three Woori Finance Holdings Co Ltd's units including the country's largest securities brokerage by assets.
Woori Investment & Securities Co Ltd gained 0.5 percent.
Steelmaker POSCO and tobacco manufacturer KT&G Corp rose 1.2 percent and 1.3 percent, respectively.
Institutional investors purchased a net 174.3 billion won ($164.54 million) in local shares, and were on track to be net buyers for a 15th straight session.
($1 = 1059.3000 Korean won) (Reporting by Jungmin Jang and Joyce Lee; Editing by Richard Borsuk)