South Korea's military says its northern neighbor has fired two medium-range ballistic missiles. The country's analysts suspect the launch involved research on solid fuel engines that the North's military recently tested.

South Korean military officials say Pyongyang launched them from near Tongchang-ri in the country's northwest, in an easterly direction at 11:13 a.m. and 12:05 p.m. on Sunday.

Japan's Defense Ministry says both missiles flew about 500 kilometers with a maximum altitude of 550 kilometers. The missiles apparently landed outside of Japan's exclusive economic zone in the Sea of Japan.

A medium-range ballistic missile can hit targets 1,000 to 3,000 kilometers away. South Korea's defense white paper says the North's submarine-launched ballistic missile called "Pukguksong" and "Pukguksong-2" that were modified for land-based launch are the same type.

North Korea announced on Friday that it successfully tested a high-thrust solid-fuel engine the previous day.

South Korean media report that the latest test firings are a response to Japan's approval of three key documents to revamp its defense strategy on Friday.

The North has fired missiles with unprecedented frequency this year. Japanese officials say its latest action marks the 35th occasion in 2022 when missiles were launched, including cruise missiles.

16 of these were from late September to the end of November. Pyongyang says it fired a new intercontinental ballistic missile on November 18th.

Japanese State Minister of Defense Ino Toshiro said, "A series of actions by North Korea that rapidly escalates provocations and threatens the peace and security of Japan and the international community cannot be tolerated. It violates relevant Security Council resolutions. Japan lodged a strong protest with North Korea through its embassy in Beijing, and strongly condemned North Korea."

The state minister of defense says the government will work closely with the United States, South Korea, and other countries concerned to deal with the situation.