* BOJ's move quickly taken in stride
* Nikkei falls 0.5 percent for the week
* Put-call ratio rising on geopolitical tension
By Ayai Tomisawa
TOKYO, July 7 (Reuters) - Japan's Nikkei share average dropped to a three-week low on Friday after global shares tumbled, although investors quickly took in stride the Bank Of Japan's decision to raise 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 market then trimmed the losses as the weakened yen supported overall sentiment, but investors moved past the decision and focused on major global events before the market closed.
The Nikkei dropped 0.3 percent to 19,929.09, the lowest closing point since June 15. For the week, the Nikkei dropped 0.5 percent.
A sharp sell-off in both U.S. and European shares overnight sapped investors' risk appetites.
Wall Street retreated after disappointing labour market data clashed with the possibility of a more hawkish Federal Reserve. Markets are focused on U.S. jobs data due out later in the day.
Investors also remain cautious with rising yields in Europe on bets the European Central Bank is moving ever closer towards unwinding its massive monetary stimulus.
"There are fears about the end of lose monetary policy in the global market," said Isao Kubo, equity strategist at Nissay Asset Management.
Fridays notable losers domestic-demand sensitive stocks such as real estate firms and construction companies. Mitsui Fudosan Co and Mitsubishi Estate Co dropped 2.3 percent and 2.2 percent, respectively.
Kajima Corp shed 2.3 percent and Taisei Corp declined 1.3 percent.
Also keeping investors on the back foot is simmering 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 have cast a cloud over the Japanese market for now, 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 0.5 percent to 1,607.06. (Editing by Shri Navaratnam)