South Korea's unification ministry said Wednesday that the country was closely monitoring "possible provocation" of the Democratic People's Republic of Korea (DPRK) after Pyongyang's warning of preemptive missile strikes against the U.S. island of Guam in the Pacific.

Seoul's unification ministry spokesman Baek Tae-hyun told a press briefing that the authorities of South Korea and the United States were closely watching relevant moves in preparation for the DPRK's "further provocation."

Baek said the South Korean military authorities maintained a complete defense readiness in preparation for several possible situations, noting that it would be important for the DPRK "to stop provocation and change attitude."

The remarks followed the DPRK's warning of preemptive missile strikes against the U.S. military base of Guam in response to two U.S. strategic bombers which were sent again Tuesday to South Korea.

Earlier in the day, the spokesman of the Strategic Force of the Korean People's Army (KPA) of the DPRK was quoted by the official Korean Central News Agency (KCNA) as saying the military was examining an operational plan for an enveloping missile strike at areas around Guam with its intermediate-range ballistic missiles, called Hwasong-12.

According to the KCNA report, the U.S. military flew two B-1B bombers, which are based on the U.S. Anderson Air Force Base in Guam, Tuesday over the Korean Peninsula. The bombers have been "threatening and blackmailing" the DPRK through their frequent visits to the sky above South Korea, the KCNA said.

Just hours before the DPRK's strike warning, U.S. President Donald Trump warned Pyongyang that if it continues to threaten the U.S., the DPRK would face "fire and fury" the world has never seen.