RPT-Seoul shares tumble to one-month low in weeklong loss

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* KOSPI falls for fourth session to one-month low * Central bank rate cut has little impact * Samsung Elec shares end in retreat after late selling By Somang Yang

SEOUL, Oct 11 (Reuters) - South Korean shares continued their week-long fall on Thursday as investors remained pessimistic about the global economic outlook.

The Korea Composite Stock Price Index (KOSPI) closed down 0.78 percent at 1,933.09 points, the lowest since Sept 11, before the Fed announced quantitative easing measures.

"This week was a real test for the KOSPI as the IMF and World Bank warnings on the world economy dampened investor sentiment, said Cho Byung-hyun, an analyst at Tongyang Securities.

Cho predicted that the index could make a comeback if the U.S. property market figures next week are strong, but until then, the KOSPI will continue to struggle.

South Korea's central bank cut interest rates on Thursday morning as expected, but the move had little effect on the market.

Trading accelerated in the late session as options expired, resulting in selling pressure on index heavyweights.

Shares in Samsung Electronics fell as far as 2.7 percent in late session, recovering later to close 1.6 percent lower.

While most large cap shares retreated in line with the index, Korea Electric Power Corp (KEPCO) bucked the trend. Shares in the state-owned utility gained 1 percent, recovering from a $550 million block sale that weighed shares down on Tuesday .

Decliners outnumbered gainers 481 to 344.

The KOSPI 200 benchmark of core stocks closed down 0.9 percent, while the junior KOSDAQ edged 0.2 percent higher.

Move on day -0.78 percent 12-month high 2,057.28 14 March 2012 12-month low 1,750.60 19 Dec 2011 Change on yr 5.88 percent All-time high 2,231.47 27 April 2011 All-time low 93.10 6 January 1981 (Editing by Eric Meijer)

((somang.yang@thomsonreuters.com)(+82 2 3704 5643)(Reuters Messaging: somang.yang.thomsonreuters.com@reuters.net))