An ethnic slur hurled by a riot police officer at a group of anti-base protesters in Okinawa has sparked a bitter exchange between the governor of the prefecture and his counterpart in Osaka, from where the officer was dispatched.

Okinawa Gov. Takeshi Onaga told a news conference that Osaka Gov. Ichiro Matsui "lacked consideration for the Okinawan people," after Matsui expressed appreciation for the work of his police officers on Wednesday, a day after one of them called the protesters dojin, a Japanese word meaning aboriginal that carries derogatory connotations.

Matsui said Thursday the demonstrations were "far too radical" and defended the officer in question.