The benchmark Nikkei index rose nearly 2 percent Tuesday, as the yen tumbled after a senior U.S. Treasury official backed Japan's efforts to fight deflation and boost growth, while investors largely shrugged off reports about North Korea's nuclear test.
The 225-issue Nikkei stock average gained 215.96 points, or 1.94 percent, from Friday to 11,369.12. The broader Topix index of all first section issues on the Tokyo Stock Exchange was up 11.15 points, or 1.16 percent, at 968.50.
Financial markets in Japan were closed Monday due to a national holiday.
Gainers were led by tire makers, securities firms and banks, while oil, mining and textile issues declined.
The Nikkei rose more than 300 points at one stage, as the dollar jumped to the lower ¥94 range on comments by U.S. Undersecretary of Treasury for International Affairs Lael Brainard expressing support for the economic policies of Prime Minister Shinzo Abe, dubbed "Abenomics," brokers said.
"We support the effort to reinvigorate growth and to end deflation in Japan," Brainard told reporters at the Treasury Department.
It is the first time that a senior U.S. official has voiced support for Abe's economic policies.
"Market players were cautious about any comment warning of the yen's weakness ahead of the meeting of financial chiefs from the Group of 20 advanced and emerging economies" to be held in Moscow from Friday, but the remark by Brainard eased some concerns, triggering selling of the yen, said Hiroichi Nishi, assistant general manager of equity research at SMBC Nikko Securities Inc.