Tokyo stocks off 0.64%, nuclear fears weigh

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The Nikkei 225 index slipped 61.35 points, or 0.64 per cent, to 9,474.78 in early trade on Monday. The Topix index was off 1.59 points, or 0.19 per cent, to 855.79.

Dangerous levels of radiation detected in water thought to be leaking from a stricken reactor have dealt a setback to efforts to avert a nuclear disaster at the stricken Fukushima Daiichi plant.

Radiation in puddles near reactor two at the plant was more than 1,000 millisieverts per hour, forcing the evacuation of workers toiling to restore the cooling systems, operator Tokyo Electric Power (TEPCO) said.

The plant's cooling systems were crippled by the March 11 9.0-magnitude quake and the devastating tsunami it unleashed, which tore into the northeast coast and erased entire towns.

A shallow 6.1 magnitude aftershock jolted Miyagi prefecture on the northeast coast early Monday, triggering a tsunami warning that was later lifted. Japan has been hit by hundreds of aftershocks since the devastating March 11 quake.

"While last week was mostly about buying back of shares following the post-earthquake sell-off, investors will be paying a closer look at the specific fallout (on corporations) from the quake," Yutaka Miura, a technical senior analyst at Mizuho Securities, told Dow Jones Newswires.

Investors were also eyeing key data this week, with Japan industrial output data due Wednesday and a US jobs report on Friday.

The yen was trading at 81.52 to the dollar on Monday from 81.34 yen on Friday, with the dollar buoyed by news the US economy grew 3.1 per cent in fourth quarter 2010, up from a previous estimate of 2.8 per cent.

The yen was at 114.46 to the dollar, from 114.60 yen Friday.