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* BOJ's move triggers turnaround in weak exporters
* Nikkei on track to fall 0.3 percent for the week
* Put-call ratio rising on geopolitical tension
TOKYO, July 7 (Reuters) - Japan's Nikkei share average dropped to a three-week low on Friday morning after global shares tumbled, but investors wasted no time trimming losses after the Bank Of Japan raised its purchases of government bonds in its market operations.
In a move aimed at stemming a rise in yields, the central bank on Friday offered to buy an unlimited amount of 10-year JGBs at a yield of 0.110 percent and also increased its buying of five- to 10-year JGBs through an auction to 500 billion yen from 450 billion yen.
The Nikkei dropped 0.1 percent to 19,979.72 in midmorning trade, after falling to as low as 19,856.65 earlier, the lowest point since June 15. For the week, the Nikkei is on track to fall 0.3 percent.
"The BOJ showed its intent on rising bond yields, which triggered the yen to weaken that was positive for the stock market," said Norihiro Fujito, a senior investment strategist at Mitsubishi UFJ Morgan Stanley Securities.
The central bank's move quickly triggered a turnaround in currency-sensitive exporters, such as automakers and tech companies, which fell initially after a sharp decline in Wall Street soured sentiment.
Toyota Motor Corp rose 1.1 percent, Nissan Motor Co added 0.7 percent and Tokyo Electron gained 1.0 percent.
The dollar soared 0.6 percent to 113.82 yen, compared with 113.11 yen earlier.
On the other hand, domestic-demand sensitive stocks languished. Real estate companies Mitsui Fudosan Co and Mitsubishi Estate Co both dropped 1.4 percent.
Construction shares also underperformed. Kajima Corp shed 1.9 percent and Taisei Corp declined 1.2 percent.
Wall Street retreated after disappointing labor market data clashed with the possibility of a more hawkish Federal Reserve.
That said, investors are cautious with rising yields in Europe on bets the European Central Bank is moving ever closer towards unwinding its massive monetary stimulus.
Also making investors wary is ongoing tension in the Korean peninsula after North Korea's launch this week of what it said was a nuclear-capable intercontinental ballistic missile.
Before the G20 summit on the weekend, Japan, the United States and South Korea agreed to push for China to play a larger role in reining in North Korea's nuclear ambitions.
Mutsumi Kagawa, chief global strategist at Rakuten Securities, said the geopolitical risks were a cloud over the Japanese market for the time being, with the Nikkei's put-call ratio - viewed as an indicator of investor sentiment - rising since earlier this week.
The ratio is calculated by dividing the number of traded put Nikkei options by the number of traded Nikkei call options.
"The rising put-call ratio reflects investors' cautious stance in the market, which reminds us about the geopolitical tensions in the region in the spring," Kagawa said.
The broader Topix dropped 0.2 percent to 1,613.01. (Editing by Jacqueline Wong)