The legislation reinterprets Article 9 of Japan's pacifist post-World War II Constitution. That section reads, in part, "the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes."

Now, the Japanese military, known as the Self-Defense Forces, or SDF, will be allowed to provide limited defense for its allies in conflicts abroad. The forces have traditionally been restricted to humanitarian roles.

The 148-90 vote was the final hurdle for the measures, which will go into effect within roughly the next six months. The lower parliamentary chamber passed the legislation in July.

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Neighbors worry

China's Ministry of Defense accused Japan of clinging to a "Cold War mentality," while media outlets noted the measures were passed a day after the 84th anniversary of Japan's invasion of China.

On September 18, 1931, an explosion destroyed a section of railroad owned by a Japanese company in the Chinese city of Mukden. Japan blamed Chinese nationalists for the blast and used it as a pretext to invade several northeastern provinces. Japanese troops occupied the region for the next 14 years.

"We will pay close attention to Japan's next moves," the Chinese ministry said in a statement Saturday. "We urge Japan to learn hard lessons from history, take seriously the security concerns of its Asian neighbors, stick to the path of peaceful development, and do more to promote regional peace and stability."

South Korea also reacted to news of the policy shift. In a Foreign Ministry statement published by Yonhap News Agency, Seoul called on its neighbor to remain dedicated to the spirit of peace. "In deciding and implementing defense and security policy down the road, Japan will have to do so with transparency and in the direction of contributing to regional peace and stability, while maintaining the spirit of the pacifist constitution," the statement read.

Seoul has kept a wary eye on Japan's political maneuvering. There are still painful memories of Japan's colonial rule, which lasted from 1910 to 1945. Japan's military also is accused of forcing about 200,000 women, mainly from Korea and China, to serve as sex slaves in the 1930s and '40s.

The legislation, which Prime Minister Shinzo Abe championed, sparked fierce and vocal opposition within Japan. Tokyo has seen massive demonstrations over the measures in recent months. And a scuffle broke out in parliament Thursday as opposition lawmakers in a special committee of the upper house attempted to delay a vote. But the bill ultimately passed the committee, setting the stage for Saturday's vote.

The argument for the legislation

Supporters of the legislation, including top U.S. officials, said Japan needs to expand the role of the Self-Defense Forces to counter potential threats from China and North Korea. Both countries continue to develop their military and nuclear weapons programs.

Tokyo has faced international pressure to expand the role of its military in a way that allows it to defend the interests of its key allies, including the United States. America is bound by treaty to defend Japan.

The argument against

But the proposed changes triggered outrage on the streets of Tokyo. Opponents of the legislation said seven decades of Japanese postwar pacifism were tossed away without proper public debate or discourse. Tens of thousands of anti-war demonstrators gathered in recent weeks outside the Japanese parliament building -- the largest protests of their kind in Japan in more than 50 years.

The Prime Minister has grown increasingly unpopular in recent months for doggedly pushing the controversial security bills through parliament. During protests against the changes to Article 9, his face appeared on posters with a Hitler-style mustache and Nazi swastika drawn on his forehead.

Sweeping government powers?

While the security legislation may strengthen Japan's ties with its allies, Koichi Nakano, a professor at Sophia University, warns it also gives "very sweeping powers to the government," which could allow logistic support and assistance to allied countries during wartime.

He said that Abe's administration has rushed discussion of the security legislation, and that the public demands "the government to slow down so that people get a better understanding of what is happening."

Opposition to the move is clearly evident in opinion polls. A recent poll carried out by Japanese newspaper Asahi Shimbun indicated that 54% of respondents opposed the legislation, while 29% supported it. Three-quarters of respondents said parliamentary debate on security measures has been insufficient.

Economic costs

There is also concern about the potential impact of the legislation on Japan's defense budget at a time when the nation is struggling with a crippling national deficit and chronic economic stagnation.

The expansion of Self-Defense Forces missions could spur increases in defense spending. Japan's Ministry of Defense submitted a 5.09 trillion yen ($41.7 billion) request for budget allocations for the coming fiscal year, a 2.2% increase from 2015.

CNN's Yoko Wakatsuki, Jason Hanna, Chieu Luu, Pierre Meilhan and Kathy Novak contributed to this report.