TOKYO —  Japan's air force has never spotted a UFO, but the country's top government spokesman said Tuesday he "definitely" believes they exist.

Chief Cabinet Secretary Nobutaka Machimura was speaking to reporters in response to demands lodged by an opposition lawmaker for an inquiry into "frequent reports of UFO sightings."

The government said in an official reply that it had "not confirmed sightings of unidentified flying objects believed to be from outer space."

Still, "I definitely believe they exist," Machimura said as reporters erupted in laughter.

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In a written response issued Tuesday to opposition Democratic Party of Japan lawmaker Ryuji Yamane, the government said the air force had often spotted "birds and other objects beside aircraft," but no UFOs.

Tokyo keeps a vigilant watch over Japanese airspace and is ready to scramble fighter jets to intercept suspicious airborne objects, the government reply said.