Japan's Nikkei share average struck a fresh four-week intraday low on Wednesday morning after weak U.S. manufacturing data and construction spending added to concerns about a global economic slowdown.

A risk-off atmosphere pervaded as some market players worried about a lack of detail in the European Central Bank's plan to bring down high borrowing costs for heavily indebted Italy and Spain, which it is expected to unveil at its meeting on Thursday.

The Nikkei <.N225> edged down 0.5 percent to 8,735.90, breaking below support at its 75-day moving average of 8,768.78.

Komatsu Ltd <6301.T> dropped 1.4 percent and Hitachi Construction Machinery Co Ltd <6305.T> lost 1.3 percent after U.S. construction spending in July fell by the most in a year, reinforcing fears of flagging growth in the world's largest economy.

"The figures are not good and I think it makes investors even more keen to watch what happens with the U.S. jobs data out on Friday, which may well determine the Fed's decision on further stimulus at the FOMC next week," said Masashi Oda, chief investment officer at Sumitomo Mitsui Investment Trust.

Index heavyweight Fast Retailing Co Ltd <9983.T> also weighed on the Nikkei, falling as much as 1.6 percent to a three-week low after its Uniqlo stores reported a 2 percent increase in August domestic same-store sales, coming in below market expectations.

Shares of cash-strapped computer services provider NEC Corp <6701.T> fell 1.8 percent after a Reuters report that the company would sell its entire stake in China's Lenovo Group Ltd <0992.HK> for about 18 billion yen ($230 million).

Bucking the market, Chubu Electric Power Co Ltd <9502.T> rose 4.8 percent after the utility said it would begin paying an annual dividend of 50 yen in the year ending March 2013, despite forecasting an operating loss of 45 billion yen ($574 million) in the same period.

"Chubu is very aware that it needs to entice or appease its shareholders because its share price has fallen so much it will have to issue more bonds," Oda said. "It was also the electric power company with the lowest reliance on nuclear power so it has a more stable income than the others."

Chubu's gains pushed the electric and gas subindex <.IEPNG.T> up 0.5 percent, making it the best-performing sector on the Topix. However, it is down 26 percent this year after falling 44 percent in 2011, as utilities have been hit by soaring bills for oil and natural gas as most of Japan's nuclear reactors remain offline.

The broader Topix <.TOPX> dropped 0.5 percent to 722.91. ($1 = 78.3900 Japanese yen)

(Reporting by Sophie Knight; Editing by Chris Gallagher)