Japan conveyed 'grave concerns' to both Russia and China through diplomatic channels, said Japanese defence minister Nobuo Kishi.
He characterised the incident as "a likely provocation by both Beijing and Moscow on a day when US President Joe Biden", Indian Prime Minister Narendra Modi and Australia's newly elected leader, Anthony Albanese, were meeting in Tokyo.
'We believe the fact that this action was taken during the Quad summit makes it more provocative than in the past,' he said, adding it was the fourth such incident since November.
Russian and Chinese jets had also entered South Korea's air defence identification zone earlier in the day.
