Military authorities here only detected the noise of North Korean coastal artillery rounds being fired on Nov. 23 in flagrant breach of a September 2018 cross-border agreement.

Even though it was the ninth anniversary of the deadly shelling of Yeongpyeong Island, officers were unable even to figure out where the noise was coming from, let along determine the number of rounds fired or the trajectory of the projectiles.

That North Korean leader Kim Jong-un was actually there to observe the drill also completely escaped the South Korean military's notice, even though it was ostensibly monitoring the North's communications networks.

According to a briefing the Defense Ministry gave to Liberty Korea Party lawmaker Baek Seung-joo, military authorities heard the sound of artillery rounds being fired on Saturday morning but were unable to find out any more information and only learned about the details from the North Korean state media two days later.

"It was difficult to specify the direction, impact point or number of rounds fired," the ministry said.

The ministry said it strongly protested against the firing drill both verbally and in a fax sent to the North on Monday.

