Japanese defense ministry officials said on Tuesday that eight Chinese jets flew over the Tsushima Strait in western Japan on Monday.
The officials said fighters from Japan's Air Self-Defense Force were scrambled.
The Chinese aircraft did not violate Japan's airspace, Japan's NHK World reported.
The ministry officials said the Chinese aircraft were six H-6 bombers, plus an early-warning plane and an intelligence-gathering plane.
They also said the Chinese planes headed northeast over the Sea of Japan (East Sea) and later made a U-turn and flew back to the East China Sea.
South Korea's Yonhap News Agency earlier reported that around 10 Chinese planes also entered the Korean air defence identification zone for five hours on Monday, prompting South Korea to launch "a sortie of fighter jets", and send a warning signal to the Chinese planes.
Yonhap said these planes flew near a submerged rock located off the southern coast of Jeju island "several times".