SEOUL (REUTERS) - North Korea appeared to have fired a short-range multiple rocket launcher on Sunday (March 20), South Korea's military said, amid heightened military tensions on the peninsula after a spate of larger missile launches by the nuclear-armed North.

While they garner much less attention than the massive intercontinental ballistic missiles (ICBMs), North Korea has displayed several new types of multiple launch rocket systems in recent years, adding to an already large arsenal of artillery and rockets ideal for potentially striking targets in the South.

"This morning there was firing in North Korea which is assumed to be multiple rocket launcher shots, and our military was monitoring the related situation and maintaining a readiness posture," South Korea's Joint Chiefs of Staff said in a statement, without elaborating.

North Korea's military fired four shots around 7.20am (6.20am Singapore time) for about an hour toward its west coast from an unidentified location in South Pyongan Province, Yonhap news agency reported.

South Korea's National Security Council held an emergency vice-ministerial meeting over the launches.

Last year South Korea approved plans to pursue a US$2.6-billion (S$3.53 billion) artillery interception system, similar to Israel's "Iron Dome", designed to protect against North Korea's arsenal of long-range guns and rockets.

About half of South Korea's 52 million people live in the capital Seoul and the surrounding areas, within range of the neighbour's long-range guns and multiple rocket launchers.

Pyongyang has conducted an unusually high pace of missile launches this year.

South Korea and the United States warn that the North could resume test-firing its largest ICBMs for the first time since 2017 amid stalled denuclearisation talks.

North Korea also appears to be preparing to launch a spy satellite, and new construction has been spotted at its shuttered nuclear test site.