Tokyo: North Korea fired some 130 artillery shells into eastern and western maritime "buffer zones" on Monday in violation of a 2018 bilateral military agreement, Yonhap News Agency reported, citing South Korea's military.

The Joint Chiefs of Staff (JCS) said that it detected the artillery firings, thought to involve multiple rocket launchers, from Kangwon Province and South Hwanghae Province, from 2:59 p.m. (0559 GMT).

The shells splashed into the maritime buffer zones north of the Northern Limit Line, a de facto sea border, which were set under an inter-Korean military accord signed on Sept. 19, 2018, to reduce border tensions.

The JCS communicated warnings to the North multiple times, pointing out the violation of the military accord and calling for the immediate cessation of the provocation. "The artillery firings into the eastern and western maritime buffer zones are a clear violation of the Sept. 19 military accord and we strongly urge the North to immediately halt them," the JCS said.

It added that the South Korean military is tracking and monitoring related North Korean movements in cooperation with the US and is strengthening a readiness posture in preparation against a potential contingency.