KCNA, the North's official news agency, said on Tuesday that North Korea had instructed its military units to fire more artillery shells into the sea in response to South Korea's ongoing exercises across the border.

A day prior, North Korea claimed to have shot more than 130 shells into the sea off its east and west coastlines, some of which landed in a buffer zone near the sea border between the two Koreas. This was a violation of a 2018 inter-Korean agreement to calm hostilities, according to Seoul.

Since Monday, South Korean and American forces have been conducting live-fire drills along the border. The allies argue that the drills are required to discourage a nuclear-armed North Korea, which has conducted a record number of missile tests this year and is preparing to resume nuclear testing for the first time since 2017.

Pyongyang has harshly denounced the joint exercises as provocative and evidence of hostile intentions by South Korea and the United States.

According to KCNA, a spokesman for the North Korean army stated, "The enemy must immediately discontinue provocative military measures in the area near the front lines."

In addition to the artillery fire, the North Korean army issued a combat emergency notice to all levels of units and instructed forces to increase surveillance, according to a spokeswoman.