"We have not seen any visible powerful seismic events. If there were weak ones, they did not surpass the threshold and were not displayed on [our equipment] so we did not feel them", the spokesperson said.
The specialist noted that the equipment registered seismic events of the average magnitude of at least two points on the Richter scale.
According to the regional meteorological service, the radiation background in the area on Friday is 12-13 micro roentgen per hour, while the permissible level is 30 micro roentgen per hour.
Earlier in the day, the South Korean Joint Chiefs of Staff (JCS) said North Korea had fired two unidentified projectiles from its eastern Tongchon area in the Kangwon province. The projectiles flew in the direction of the Sea of Japan.
Friday's launch is the sixth projectile launch by North Korea since 25 July.
The country previously fired what the JCS called a short-range ballistic missile last Saturday. However, Pyongyang said on Sunday that it had tested a "new weapon system".
Notably, the UN Security Council has prohibited North Korea from developing its ballistic missile program.
The launches come amid North Korea's protests against US-South Korean joint military drills and deadlocked US-North Korean denuclearization talks.