A once fringe opposition party in Japan has become the fourth largest in parliament by pushing a nationalist "Japanese First" agenda.

Sanseito leader Sohei Kamiya's xenophobic views, antisemitic remarks and emphasis on Japan’s ethnic purity have raised alarms.

Japan's far-right populist Sanseito party was one of the biggest winners in the weekend's upper house election, attracting many voters with its “Japanese First" platform that included calling for tougher restrictions on foreigners and the curtailment of gender equality and diversity policies.