North Korea says the medium long-range strategic missile it tested over the weekend can carry a nuclear warhead.

The country’s official Korean Central News Agency says the missile fired Sunday Korea time was a Hwasong-12 “capable of carrying a large-size heavy nuclear warhead.”

The South Korean, Japanese and U.S. militaries say the missile flew for half an hour and reached an unusually high altitude before landing in the Sea of Japan. Tokyo says the flight pattern could indicate a new type of missile.

Japanese officials say the missile flew for about 30 minutes, traveling about 500 miles and reaching an altitude of 1,240 miles.