Kim Jong-un, top leader of the Democratic People's Republic of Korea (DPRK), guides the firing of three ballistic missiles from the western region of Hwangju in North Hwanghae province, July 19, 2016. [Photo/IC]

PYONGYANG -- Top leader of the Democratic People's Republic of Korea (DPRK) Kim Jong-un has guided a test firing of a ballistic rocket of the Hwasong artillery units of the strategic force of the military, the official news agency KCNA reported Wednesday.

The test-firing was conducted under simulated conditions of launching preemptive strikes at the ports and airfields in South Korea where the US nuclear hardware is to be mobilized, the KCNA said.

The test also "examined the operational features of the detonating devices of nuclear warheads mounted on the ballistic rockets at the designated altitude over the target area," it added.

Kim was satisfied with the test result and instructed to ensure the speed and security of the operation of nuclear attack system and develop diversified ballistic rockets.

The date and place of the test-firing was not given by the state media.

South Korea's Joint Chiefs of Staff (JCS) said Tuesday that the DPRK fired off three ballistic missiles, which are believed to have been a Scud-C type, from the western region of Hwangju in North Hwanghae province between 5:45 a.m. and 6:05 a.m. Seoul time.

The missiles traveled about 500 to 600 km, making them able to hit the entire South Korean region, said the JCS.

The test-launch came six days after Seoul and Washington agreed to deploy the Terminal High Altitude Area Defense (THAAD) in Seongju county, some 250 km southeast of Seoul, by the end of next year.

The DPRK's military threatened to take "physical measures" against THAAD when the deployment site is determined in response to the THAAD deployment decision.

Meanwhile, Seoul's unification ministry said Monday that Pyongyang appeared to have been in a state of preparing another nuclear test given increased activity in its main Punggye-ri nuclear test site where the country carried out four underground nuclear tests since 2006.