Campaigning was heating up for Japan's July 10 upper house election on Saturday, with ruling and opposition party leaders pointing to rising prices of daily needs as a major issue.

Entering the first weekend after the election's official campaigning kicked off Wednesday, Prime Minister Fumio Kishida and his rivals delivered stump speeches mainly in closely contested voting districts across Japan.

Kishida, who heads the Liberal Democratic Party, blamed Russia's invasion of Ukraine for high energy and other prices. "To protect your livelihoods and work, the government will take full responsibility and do its utmost to take measures against price increases," he said in Kofu, Yamanashi Prefecture.

Kishida, who will attend meetings with world leaders in Germany and Spain next week, later returned to Tokyo, where the LDP and the main opposition of the Constitutional Democratic Party of Japan are fielding two candidates each to vie for six seats up for grabs in the capital's district.

Prime Minister Fumio Kishida delivers a speech in Kofu, Yamanashi Prefecture, on June 25, 2022. (Kyodo)

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Kenta Izumi, leader of the main opposition party, facing an uphill battle in the triennial House of Councillors election, criticized the government's economic policy.

"The prime minister has not looked straight at price rises and also has no concrete measures," Izumi said in the major southwestern city of Fukuoka. "Let's raise our voice and change politics."

Natsuo Yamaguchi, chief of the LDP's coalition partner Komeito, participated in a rally for young people in Nagoya, pledging to invest more in cultivating human resources and achieving sustainable wage increases.

"We will do the same administrative and fiscal reforms in Japan that we have done in Osaka," Nobuyuki Baba, co-leader of the opposition Japan Innovation Party, said in a speech in Tokyo.

Japanese Communist Party leader Kazuo Shii, speaking in Narashino, Chiba Prefecture, slammed the Kishida administration's plan to bolster Japan's defense forces, saying, "Let's use everyone's power to stop politics that crushes our lives."