South Korea's military says North Korea has fired artillery shells toward the sea off the Korean Peninsula for the second straight day.

South Korea's Joint Chiefs of Staff said the North fired about 100 artillery shells toward the Yellow Sea, west of the peninsula, from the southwestern province of South Hwanghae, starting at around 12:30 p.m. on Wednesday.

The two countries agreed in 2018 not to fire artillery into the maritime buffer zone, which serves as a de facto inter-Korean maritime border.

But the South says it has confirmed that the North fired the shells into the zone.

North Korea has conducted a series of similar shelling since Friday, including the one late on Tuesday.

The Joint Chiefs of Staff denounced the North's shelling as an act that undermines peace and stability of the international community. It urged Pyongyang to immediately halt the shelling.

Meanwhile, North Korea describes its shelling as "a threatening, warning fire" in response to South Korea's ongoing military drills.

A spokesperson for the General Staff of the North's Korean People's Army issued a statement right after Wednesday's artillery shelling.

The statement said the latest shelling is a countermeasure to the South's artillery rocket launches. It said the North's military ordered shelling toward the east and west of the Korean Peninsula.

North Korea's state-run media also published footage which it says shows the firing of South Korea's artillery rockets.