Two Hyunmoo-2 missiles were launched from a site near the inter-Korean border six minutes after the North fired a missile from the Sunan district of Pyongyang, Yonhap reported Friday citing the South Korean military.

One of the South Korean missiles “accurately hit” a simulated target in the East Sea some 250 kilometers away, according to a Joint Chiefs of Staff (JCS) official. The other fell into water during the initial stage of the flight.

According to the report, the launch was performed while the North Korean missile was still in the air. The South Korean Defense Ministry explained that it was able to make an on-the-fly response because it had detected the North’s preparation for a launch in advance.

Earlier in the day, it was reported that had Pyongyang launched another missile, the 15th North Korean missile test this year.

The unidentified projectile was heading east, according to published reports, after leaving the launch pad around 6:57 a.m. local time. The missile flew for about 20 minutes until falling into the Pacific Ocean at 7:16 a.m. about 2,000 kilometers east of Hokkaido, NHK reported citing Japanese government officials.

The South Korean Office of the Joint Chiefs of Staff reports that American and South Korean personnel are currently investigating the details of the launch.

The new North Korean missile launch came just days after the UN Security Council approved sanctions against Pyongyang over its missile and nuclear program. On September 3, the North conducted its most powerful ever nuclear test, which many believe to be an H-bomb.