Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, said North Korea conducted an intermediate-range strategic missile drill Saturday, claiming its maneuvering flight prevented South Korean and Japanese militaries from tracking its full trajectory.

“At dawn of this morning, a drill of firing a strategic weapon toward the East Sea of Korea was conducted,” she said in a statement issued through the state-run Korean Central News Agency (KCNA).

Her statement combined an account of the launch with mockery of Seoul and Tokyo’s tracking capabilities, presenting their reportedflight distances as evidence of North Korean technological superiority