By Michael Kitchen, MarketWatch

LOS ANGELES (MarketWatch) -- Asian stock markets ended lower Wednesday after overnight losses in the U.S. on monetary-policy concerns, with Japan shares falling the most in nearly two months as exporters took a heavy hit from the yen's advance.

The blue-chip Nikkei Stock Average plunged 4% in Tokyo, its worst one-day percentage loss since June 13, while Australia's S&P/ASX 200 fell 1.9%, and South Korea's Kopsi gave up 1.5%.

Hong Kong's Hang Seng Index also retreated 1.5%, while the Shanghai Composite Index slid 0.7% after a swinging in and out of gains.

The moves came amid seasonally thin trading, with Kim Eng Securities strategist Andrew Sullivan predicting "light volumes to remain." He noted some market holidays this week in Southeast Asia for the end of Ramadan likely to make volumes "lighter still."

"Summer doldrums seem to be upon us," he said.

The weak tone in Asia followed a second day of losses for U.S. benchmarks, with the S&P 500 (SPX) sliding back below the 1,700 level after ending the day down 0.6%.

Concerns about the Federal Reserve's stimulus outlook helped drive the drop on Wall Street, after Chicago Fed President Charles Evans said he expects the central bank to begin tapering its asset-purchase program by the end of the year.

Japanese equities took an additional hit from the yen, as the U.S. dollar (USDJPY) fell as low as Yen96.74, according to FactSet, after having traded above the Yen98 level just over 24 hours earlier.

The higher yen hit exporters, which have benefitted from a weaker currency.

Among them, Sony Corp. (SNE) lost 4.3%, Tokyo Electron Ltd. (8035.TO) retreated 6.7%, and Olympus Corp. (OCPNF) slid 4.7%.

Shares of Suntory Beverage & Food Ltd. , which debuted in Tokyo last month, gave up 2.9% of their value despite almost doubling its fiscal first-half profit.

Audio-tech firm Pioneer Corp. (6773.TO) tumbled 8.7% after reporting a wider quarterly loss and slashing its fiscal-year profit outlook by more than 90%.

But on the upside, energy major Showa Shell Sekiyu K.K. surged 3.7% after hiking its own fiscal-year profit outlook by 85%.

In Sydney, the key mining and financial sectors were both heading lower, with Newcrest Mining Ltd. (NCMGF) sinking 4.2% after benchmark Comex gold futures lost their grip on the $1,300-an-ounce level in Tuesday trade.

Fortescue Metals Group Ltd. (FSUMY) and uranium extractor Paladin Energy Ltd. (PDN.T) also helped lead mining-share losses, dropping 4.6% and 7%, respectively.

Banks extended their weakness after the Reserve Bank of Australia's Tuesday interest-rate cut, with National Australia Bank Ltd. (NAUBF) off 1.7% and Macquarie Group Ltd. (MCQEF) lower by 3%.

Chip shares traded lower in Seoul, where Samsung Electronics Co. (SSNLF) fell 2.6%, and SK Hynix Inc. (HXSCL) lost 3.6%, following a 0.7% drop for the Nasdaq (RIXF) .

Among Hong Kong stocks, the energy shares were a weak spot after crude-oil futures lost 1.2% during regular trade in New York.

Cnooc Ltd. (CEO) slid 1%, and PetroChina Co. (PTR) surrendered 2.7%, while China Petroleum & Chemical Corp. -- better known as Sinopec (SNP) -- saw a 2.4% decline.

Casino shares were mixed, with Wynn Macau Ltd. (WYNMY) rising 0.7%, but MGM China Holdings Ltd. (2282.HK) dropping 4.6% after posting a quarterly loss.

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