* Yellen, Ukraine to have limited influence
* Kospi to post 3rd winning week
By Christine Kim
SEOUL, Feb 28 Seoul shares were unchanged early on Friday in a tug-of-war as institutions sold to take profits while foreigners snapped up local stocks for a sixth straight session, capping losses.
The Korea Composite Stock Price Index (KOSPI) was flat at 1,977.99 points as of 0233 GMT, compared to Thursday's local close at 1,978.43. The Kospi is poised to mark a third consecutive winning week.
"We're seeing some investors taking a breather after the Kospi's recent rise thanks to foreigner inflows while Kospi is seeing some resistance at the 120-day moving average," said Bae Sung-young, an analyst at Hyundai Securities. The Kospi's current 120-day moving average is 1,983.58.
Bae said the South Korean stock market would see minimal impact from comments by Federal Reserve Chair Janet Yellen in the U.S. Senate on Thursday, where she which reiterated the Fed's confidence in the U.S. economy.
"The conflict in Ukraine will also have little effect on the stock market...For South Korea, China's National People's Congress and the European Central Bank's policy meeting will be key," the analyst said.
China will be holding its annual parliament meeting starting March 5 and the ECB's Governing Council meeting, where it will deliberate interest rates, will be held on March 6.
Institutions were net sellers of 50.2 billion won ($46.97 million) worth of South Korean stocks in midday, while foreigners bought a net 62.6 billion won worth.
GS Retail Co Ltd jumped 4.9 percent after local brokerage reports forecast a positive outlook for convenience stores for this year.
NHN Entertainment Corp rose 4.0 percent as investors' fears of a recently implemented regulation in web-board games in South Korea dragging down profits in the game sector subsided.
Meanwhile shares in GS Engineering & Construction Corp fell 4.0 percent on media reports it was under investigation by financial authorities.
Advancers slightly outnumbered decliners 392 to 378.
The KOSPI 200 benchmark of core stocks was down 0.04 percent, while the junior KOSDAQ edged 0.2 percent higher. ($1 = 1068.8500 Korean won) (Additional reporting by Jungmin Jang; Editing by Eric Meijer)