South Korea said that North Korea launched a small-range multi-purpose rocket launcher on Sunday. It was amidst increased tensions between the two countries, following several larger North Korean missile launches.

They are not as well known than the intercontinental missiles (ICBMs), but North Korea has demonstrated many new multiple-launch rocket systems over the past few years. These rockets have been added to its arsenal of artillery that can be used to strike South Asian targets.

“This morning there was firing from North Korea that is believed to have been multiple rocket launcher fires. Our military was monitoring this situation and maintaining readiness posture,” South Korea’s Joint Chiefs of Staff reported in a statement.

Yonhap news agency reports that North Korea’s military launched four shots at around 7:20 am (2220 GMT on Saturday). The shot traveled for an hour along its west coast, from an unknown location in South Pyongan Province.

South Korea’s National Security Council called an emergency session of its vice-ministerial members to discuss the launch.

South Korea last year approved plans for a $2.6 billion artillery intercept system. It is similar to Israel’s Iron Dome, and was designed to defend against North Korea’s long-range rocket-launched guns.

Nearly half of South Korea’s 52 million inhabitants live in Seoul, the capital and surrounding areas. They are within easy reach of their long-range guns as well as multiple rocket launchers.

This year, Pyongyang launched a record number of missiles. The United States and South Korea warn that North Korea could continue firing its biggest ICBMs, despite stalled talks on denuclearization.

North Korea may also be in the process of launching a spy satellite. A new building has also been found at its closed nuclear test site.