The South Korean military says North Korea has fired artillery shells toward the east and west of the Korean Peninsula -- the second such incident in less than a week.

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 from around 10 p.m. on Tuesday.

They also said the North lobbed about 150 rounds in the east from the southeastern province of Kangwon from around 11 p.m.

The two countries agreed in 2018 not to fire artillery into maritime buffer zones, which serve as the de facto inter-Korean maritime border. South Korea said the rounds fired by the North fell into waters on the North Korean side.

The South Korean military strongly urged Pyongyang to immediately halt the shelling, saying in a statement that "North Korea's continued provocations are actions that undermine peace and stability of the Korean Peninsula and the international community."

The North conducted similar shelling last Friday, saying the action was aimed at sending another clear message against provocations by what it called "the enemies."

The South's military has been conducting regular field maneuver exercises since Monday, which partially involve US troops. Both the US and South Korean militaries are on alert, as the firing by the North could be a response to the drills.