SEOUL -- The Democratic People's Republic of Korea (DPRK) fired two ballistic missiles Wednesday night in a simulated "tactical nuclear strike drill" in response to a US-Republic of Korea joint military exercise conducted earlier that day involving American strategic bombers, the official Korean Central News Agency (KCNA) reported Thursday.

With the Ulchi Freedom Shield military drill between the United States and ROK reaching its climax, the United States on Wednesday sent a formation of B-1B nuclear strategic bombers to participate in a joint attack exercise with ROK military aircraft over the eastern and western waters off the Korean Peninsula, said the KCNA, citing a report released Wednesday by the General Staff of the Korean People's Army (KPA).

In response, a KPA tactical nuclear operation unit based in the country's western region fired two tactical ballistic missiles from the Pyongyang International Airport on Wednesday night, in a military drill simulating a tactical nuclear attack against major command centers and operational airfields in ROK, the KCNA said.

The missiles heading northeast flew a distance before completing detonations at a preset altitude of 400 meters above a target island, an operation designed to show the DPRK's "resolute punitive will and substantive retaliation capabilities" against the military threat posed by the United States and ROK, it added.

The missile launches came one day after Kim Jong Un, general secretary of the Workers' Party of Korea and president of the State Affairs of the DPRK, inspected the training command post of the KPA General Staff on Tuesday.

Kim said during the inspection that the DPRK needs to confront the United States and ROK thoroughly, in response to the frequent military moves by the two countries which have made "a clear revelation of their scheme for invading the DPRK," the KCNA said in a separate report on Thursday.

The DPRK's top leader instructed the KPA to speed up military exercises and war preparations, the report added.

The United States and ROK kicked off their Ulchi Freedom Shield military drill on Aug 21 that were slated to last until Aug 31, according to ROK's Joint Chiefs of Staff.