* Intervention, easing impact fading -fund manager
* Oil, financials sharply down
* Nikkei breaches key 9,300-line
* Topix below 800 for first time since March 17
* Investors stay on the alert before U.S. jobs data
By Ayai Tomisawa
TOKYO, Aug 5 (Reuters) - Japan's Nikkei stock benchmark tumbled on Friday to its lowest since the immediate aftermath of the March 11 earthquake, hit by sharp falls in the U.S. market as worries over the global economy dominated the mood, offseting a boost from Japan's currency intervention and monetary easing the previous day.
The Dow and the S&P tumbled more than 4 percent on Thursday and the Nasdaq lost 5 percent on fears that the United States is staring at another recession and that Europe's sovereign debt crisis is swallowing two of its largest economies.
All the 33 subsectors on the Topix were lower, with mining and securities sectors hit by a heavy sell-off on investor reluctance to hold risky assets.
"A heavy sell-off is expected today. Negative factors are coming from overseas markets, so there's nothing Japan can do to avoid the repercussions," said Kenichi Hirano, a strategist at Tachibana Securities.
The benchmark Nikkei breached immediate support at 9,300, where the index hovered for some time after a slide that followed the March quake. The Nikkei was down 3.6 percent at 9,312.52 after hitting an intraday low of 9,264.09 soon after the open.
The broader Topix fell below the 800-mark for the first time since March 17, dropping 3.3 percent to 799.34.
Analysts also said that futures-led selling was dragging down the market, while retail investors may pick up some defensive stocks on dips.
"But such dip-buying may not have an impact on the overall market as foreigners are likely to be the main sellers," Hirano said.
The market's recent malaise stems from a number of factors. U.S. economic data has worsened, suggesting slowing growth from an already sluggish pace in the first half. Europe's sovereign debt crisis has defied remedies and threatens to engulf the large euro-zone economies of Spain and Italy.
"The selling isn't really anything like during a complete collapse, as the volumes aren't really there. People are tweaking their portfolios, but they're not really hammering their core positions all that much," said a trader for a foreign brokerage who did not want to be identified by name.
"It's more of a reaction to what happened in the U.S., risk-off globally."
IMPACT FADING
Fiscal and economic woes in Europe and the U.S. pushed up the yen near record highs on Thursday as investors sought the currency as a safe haven, prompting Japan to intervene in forex markets and ease monetary policy to relieve pain in the export-reliant economy.
But these efforts were negated by renewed concerns on the global economy after the U.S. market tumbled to reflect bearish sentiment among investors.
"It makes sense to hold Japan stocks as long as U.S. markets are strong. But as the market cautiously awaits the outcome of U.S. jobs data on Friday, people are unloading risky assets," said Fumihito Akiyama, a fund manager at Sparx Asset Management.
"The Japanese government intended to support the stock market by intervening in the foreign exchange market, but the effects of this are fading."
Japanese Finance Minister Yoshihiko Noda on Friday repeated that he was closely watching yen moves, signalling Tokyo's readiness to continue with its yen-selling intervention that media said reached a record 4 trillion yen ($50.6 billion).
Oil shares nosedived, with Inpex falling 5.9 percent to 538,000 yen and Japan Petroleum Exploration tumbling 5.0 percent to 3,580 yen after oil dropped as much as 6 percent on Thursday, with U.S. crude crashing through technical support to its lowest since February.
Pessimism in the global stock market also took its toll on financials. Nomura Holdings dropped 5.2 percent to 350 yen and Daiwa Securities fell 3.3 percent to 322 yen.
Mitsubishi UFJ Financial Group shed 3.6 percent to 378 yen and Mizuho Financial Group was down 5.5 percent at 120 yen.
(Additional reporting by Antoni Slodkowski)