North Korea on Monday fired an apparent short-range ballistic missile that is believed to have fallen into Japan’s exclusive economic zone — a move that prompted Prime Minister Shinzo Abe to vow “concrete measures” in response.

The U.S. Pacific Command said in a statement later the same day that it had detected the launch of "a short-range ballistic missile" near the eastern coastal city of Wonsan, adding that it had tracked the missile for six minutes until it landed in the Sea of Japan.

Chief Cabinet Secretary Yoshihide Suga told an emergency news conference early Monday that the missile, launched at around 5:40 a.m., is "believed to have landed in Japan's exclusive economic zone," which extends 200 nautical miles (370 km) from its coast, into the Sea of Japan.