* Fast Retailing skids after drop in same-store sales
* Nintendo tumbles on profit-taking
TOKYO, Sept 5 (Reuters) - Japan's Nikkei share average brushed one-week lows in choppy trade on Tuesday as tensions on the Korean peninsula sapped risk appetite.
The Nikkei shed 0.6 percent to end at 19,385.81 after initially opening slightly higher. It fell as low as 19,354.59, its weakest level since Aug. 29. Index heavyweight Fast Retailing dropped on weak sales.
"The biggest factor weighing on the market now appears to be uncertainty about North Korea, with investors waiting to see what happens next," said Yutaka Miura, a senior technical analyst at Mizuho Securities.
"With no way of knowing if the situation will escalate or not, many investors think it's a good time to lock in their gains," he said. South Korea said on Tuesday an agreement with the United States to scrap a weight limit on its warheads would help it respond to North Korea's nuclear and missile threat after Pyongyang conducted its sixth and largest nuclear test two days ago.
South Korea's Asia Business Daily, citing an unidentified source, reported on Tuesday that North Korea had been spotted moving a rocket that appeared to be an intercontinental ballistic missile (ICBM) towards its west coast.
On Monday, the United States accused North Korea's trading partners of aiding its nuclear ambitions and said Pyongyang was "begging for war" after signs that more missile launches were planned.
A stronger yen also weighed on shares, with the dollar sliding 0.4 percent to 109.34 yen.
Fast Retailing, the operator of Uniqlo clothing outlets, fell 0.7 percent after its domestic same-store sales slipped 3.4 percent in August from a year earlier.
Japan's bitcoin-related stocks tumbled, with Infoteria Corp shedding 9.5 percent, Remixpoint Inc down 11.2 percent, and Ceres Inc losing 7.7 percent after China on Monday banned raising funds through launches of token-based digital currencies.
Shares of Japan Airlines fell 1.1 percent after a New York-bound JAL flight returned to Tokyo's Haneda airport earlier on Tuesday, landing safely after experiencing engine trouble.
Nintendo Co was down 2.4 percent on profit-taking, moving away from a 3-1/2 week high hit last Friday.
The Mothers market of start-up shares stumbled 4.7 percent to hit its lowest in more than four months.
The broader Topix shed 0.8 percent to 1,590.71 and the JPX-Nikkei Index 400 dropped 0.7 percent to 14,109.19. (Editing by Sam Holmes and Eric Meijer)