Japanese Chief Cabinet Secretary Matsuno Hirokazu says the government has already lodged a strong protest against North Korea's missile launches through a diplomatic channel in Beijing.

Matsuno confirmed that North Korea had launched multiple ballistic missiles on Thursday morning, including what may have been an inter-continental ballistic missile.

He said none were reported to have flown inside Japan's Exclusive Economic Zone.

Matsuno added that one of the missiles, which was launched at around 7:40 am Japan time, had disappeared from radar while over the Sea of Japan.

He said no damage has been reported.

Matsuno said the National Security Council had convened, and ministers had confirmed they would continue to collect relevant information and stay on the alert for further possible missile launches.

He said Japan will work closely with the United Nations Security Council and countries including the United States and South Korea to respond to the situation.