TOKYO, July 17, 2025 (BSS/AFP) - A populist party surging in the polls ahead of Sunday's national elections in Japan has denied any ties to Russia, after one of its candidates gave an interview to Moscow state media.

Japanese politics has long been dominated by the centre-right Liberal Democratic Party (LDP), with populist groups remaining on the fringes.

But the right-wing Sanseito party is riding a wave of popular support for its inflammatory "Japanese-first" platform including opposition to globalism, immigration and foreign capital.

Opinion polls suggest it could win more than 10 upper house seats, up from two now, in an election where Prime Minister Shigeru Ishiba's coalition risks losing its majority.

Sanseito's latest controversy surrounds a rookie candidate known only as Saya, who gave Russia's Sputnik news agency an interview that was then published on its Japanese edition's X account Monday.

Saya's sudden appearance on Sputnik sparked a storm of confusion that fuelled speculation on social media that Sanseito was Russia-friendly.

Asked if the party had any special ties with Moscow, Sanseito head Sohei Kamiya told an internet news programme Tuesday: "we don't. Not at all".

"Not with Russia, China or America. We don't. We keep balanced diplomacy with any country", Kamiya said.

"To say we're pro-Russia just because she appeared on Sputnik ... I think that's just too simplistic", he said.

Kamiya attributed Saya's Sputnik appearance to "human error", saying he had no knowledge this was being organised.

He clarified that a staffer with no authority had told Saya without prior consultation with the party headquarters that she was allowed to accept Sputnik's interview request.

Sanseito's stance on Russia has come under scrutiny before, after Kamiya said Moscow shouldn't be held entirely responsible for the war in Ukraine.

"Russia's military invasion was of course bad, but there are forces in the US that drove Russia into doing that," Kamiya said Tuesday.

"So I said once that it's not fair to say Russia is the only bad guy here, and then people began saying I'm pro-Russia", he added.

Japan's Deputy Chief Cabinet Secretary Kazuhiko Aoki said Wednesday that "Japan is also becoming a target" of foreign election interference through social media and other means, according to local media reports.

The European Union has banned Sputnik along with other Russian state media for "disinformation and information manipulation".

The news agency has also been sanctioned by the United States.