Photo/Illutration People in Seoul watch news about North Korea’s missile launch on a large monitor near a train station on Oct. 2. (AP Photo)

SEOUL--North Korea is thought to have launched a ballistic missile from a submarine on Oct. 2, ramping up the security threat to Japan as SLBMs are more difficult to detect before launch.

Japan lodged a protest with North Korea the same day through its embassy in Beijing.

Condemning Pyongyang, Prime Minister Shinzo Abe said: “Firing a ballistic missile is against the U.N. Security Council resolution. We strongly protest and denounce it.”

South Korea’s Joint Chiefs of Staff announced the same day that Pyongyang launched a ballistic missile in the Sea of Japan at 7:11 a.m. from a location near Wonsan in North Korea's east coast.

South Korea’s National Security Council at the presidential office said it was likely that Pyongyang test-fired an SLBM.

It added that defense authorities in South Korea and the United States were scrutinizing the trajectory of the projectile.

Sources within the Japanese Defense Ministry concurred with the view that it was likely an SLBM, citing the fact the missile appeared to have been launched in the ocean.

The missile fell into the sea about 450 kilometers from where it was launched after reaching a maximum altitude of about 910 km, according to South Korea’s Joint Chiefs of Staff.

They said the missile was apparently in a group of North Star intermediate-range missiles.

Defense experts said the missile was launched with the apparent intention of reaching an altitude higher than usual so that it would travel over a short distance to land outside Japan’s territorial waters or territory.

If the projectile was an SLBM, it marked the first time for an SLBM to be launched by North Korea since Aug. 24, 2016, when one was fired in the Sea of Japan off the reclusive state's Hamgyongnam-do province.

SLBMs pose a bigger threat than regular ballistic missiles launched from land as they are more difficult to detect prior to an attack.

South Korea’s Defense Minister Jeong Kyeong-doo announced at the National Assembly that Seoul requested for information about the missile from Tokyo based on the General Security of Military Information Agreement between the two countries.

Although Seoul announced in August it was scrapping the pact with Japan, the current arrangement remains effective through Nov. 23.

The Japanese government announced on Oct. 2 that a ballistic missile was fired from North Korea's east coast around 7:10 a.m.

Japanese officials believe it fell in waters about 350 km off Dogojima island, Shimane Prefecture, which is within Japan’s exclusive economic zone.

Defense Minister Taro Kono said Pyongyang fired a single ballistic missile, which he said later split off, and estimated it flew in a lofted trajectory and reached a maximum altitude of 900 km.

He could not confirm whether it was an SLBM, saying that the ministry is still trying to verify the category of missile.

The latest missile is thought to be the first North Korean projectile to land within Japan’s EEZ since Nov. 29, 2017, when one fell about 250 km to the west of Aomori Prefecture.

Abe said he instructed the government to provide accurate and speedy information to the public by making all-out efforts to gather and analyze data.

Officials were also instructed to confirm the safety of vessels and aircraft and prepare for an emergency.

Then he summoned the National Security Council to discuss Japan’s response.

The director-general of the Foreign Ministry’s Asian and Oceanian Affairs Bureau discussed the matter with Steve Biegun, U.S. special envoy for North Korea over the phone.

The latest launch by North Korea followed one on Sept. 10.

At that time, the Korean Central News Agency reported that North Korea’s leader Kim Jong Un “inspected a test-firing of an extremely large rocket artillery.”