Japan's finance minister, Taro Aso, said Friday that recent moves by China to allow its currency to depreciate are a concern and could pose problems for Tokyo.
The Japanese share benchmark, the Nikkei 225 index, fell 3% to 19,435.83 on Friday, slipping below the psychological benchmark of 20,000 on selling of shares in many sectors.
"Chinese factors are a big part of this, without a doubt," Aso told reporters during a regular news briefing early in the day.
Further devaluation of the Chinese yuan could put Japan in a "tough spot," the Nikkei newspaper and other local media quoted Aso as saying.
It was unclear what sorts of choices Aso was implying Japan might make, but the Japanese currency, the yen, has fallen by over 60% against the U.S. dollar since hitting a peak of 75.35 yen to the dollar in October 2011. It was trading near 123 yen per dollar on Friday.
The yen's depreciation was hastened by massive monetary easing since 2013 by the Bank of Japan, which is buying trillions of yen in assets each month, seeking to spur growth.
The injection of massive amounts of cash into the economy drove the value of the yen lower, while in turn boosting profits of major corporations that earn a large share of their revenue overseas -- and pushing share prices higher.
The strategy is the backbone of Prime Minister Shinzo Abe's effort to staunch deflation, or falling prices due to weak demand, and spur growth by persuading consumers and companies to spend more.
The Chinese currency's decline against the U.S. dollar has had a limited direct impact on the value of the yen. But uncertainty over future policy and over the impact of China's economic slowdown is reverberating across global markets.
"It's not just China. It's the emerging markets in general," said Masamichi Adachi of JPMorgan in Tokyo.