* KOSPI slips for fifth straight session on institutions     * Won rises for second day but trades in narrow band      By Christine Kim     SEOUL, April 17 (Reuters) - The South Korean won  
  KRW=
   crawled up but was nearly flat early on Thursday after comments by the U.S. Federal Reserve chief and a positive economic view from the Fed lent some support, but Ukraine jitters kept gains in check.     Local shares also rose shortly after markets opened on sharpened risk appetite, but gains were erased by midday as institutions sold for profits.     The local currency  
  KRW=KFTC
   was quoted at 1,037.3 against the dollar as of 0207 GMT, up 0.04 percent from Wednesday's domestic close at 1,037.7.     The Korea Composite Stock Price Index (KOSPI)  
  .KS11
   was down 0.1 percent at 1,990.10 points, poised to mark its fifth day of losses.     Fed Chair Janet Yellen told the Economic Club of New York that the U.S. central bank would be delivering policy stimulus for some time to come, highlighting persistent low inflation as an immediate threat to the U.S. economy.  
  ID:nL2N0N81BD
       Her remarks, coupled with a report from the Fed that showed U.S. economic activity picked up in recent weeks supported equities early in the session.  
  ID:nW1N0LW01C
       The won is expected to trade within 1,034 to 1,040 on Thursday, according to Hong Seok-chan at Daishin Economic Research Institute.     "We are likely going to see repeated dollar sales from exporters or foreigners on the won's dips," said Hong, who added there was not enough momentum for the won to be carried above the mid-1,030 level, keeping it trapped in a tight range.     Heightened Ukraine tensions kept the won's gains capped after separatists flew the Russian flag on armoured vehicles taken from the Ukrainian army, humiliating a Kiev government operation to regain control of pro-Moscow partisan-controlled eastern towns.  
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       Foreign investors net purchased 51.6 billion Korean won ($49.73 million) worth of KOSPI shares near mid-session, while institutions sold a 27.6 billion won worth in their sixth straight session of net selling.     Stocks related to a capsized South Korean ferry were mixed early on Thursday as the search for survivors was continued for a second day.  
  ID:nL3N0N907X
       Dongbu Insurance Co Ltd  
  005830.KS
   was down 0.7 percent and Korean Reinsurance Co  
  003690.KS
   slipped 1 percent.     Meanwhile, Meritz Fire and Marine Insurance Co Ltd  
  000060.KS
  , insurer of the South Korean ferry that capsized on Wednesday up 0.4 percent, It ended up yesterday and is gaining again today on news reports that the country's regulator is going to see that insurance claims from the sinking are going to be paid out quickly.      Decliners outnumbered advancers 408 to 334.       The KOSPI 200 benchmark of core stocks  
  .KS200
   was down 0.2 percent, while the junior KOSDAQ  
  .KQ11
   edged 0.1 percent higher.     June futures on three-year treasury bonds  
  KTBc1
   added 0.04 points to trade at 105.73.                          0207 GMT   Prev close  Dollar/won            1,037.3       1,037.7  Yen/won           10.1696/756       10.1535  *KTB futures           105.73        105.69  KOSPI                1,990.10      1,992.21  * Front-month futures on three-year treasury bonds ($1 = 1037.6500 Korean Won)   (Editing by Eric Meijer)  ((christine.kim@thomsonreuters.com)(822 3704 5665)(Reuters Messaging: christine.kim.thomsonreuters.com@reuters.net))  Keywords: MARKETS KOREA/