Pyongyang has dramatically ramped up missile launches and military exercises in recent weeks, as Seoul and Washington say North Korean leader Kim Jong Un is close to conducting what would be his country's seventh nuclear test.

Roughly 250 rounds were launched late Tuesday, South Korea's Joint Chiefs of Staff (JCS) said, calling it a "clear violation" of the 2018 agreement, according to Yonhap.

"We strongly urge North Korea to immediately halt its actions," the JCS said in a statement carried by Yonhap.

"North Korea's continued provocations are actions that undermine peace and stability of the Korean Peninsula and the international community," it added.

North Korean state media did not immediately report on the incident.

The North also fired artillery rounds into the military buffer zones last week.