SEOUL, May 18 -- South Korea's top policymaker on the Democratic People's Republic of Korea (DPRK) affairs on Wednesday expressed worry about Pyongyang's possible nuclear test.

Unification Minister Hong Yong-Pyo said at a special lecture in Seoul that the DPRK conducted its fourth nuclear test on Jan. 6 and now is a crucial juncture of possibly staging the fifth nuclear detonation.

Hong said it is a high time to sternly tackle possible DPRK provocations and build a sustainable peace on the Korean peninsula.

The DPRK was widely expected here to carry out another nuclear test before or after the historic Workers' Party of Korea (WPK) congress that lasted for four days through May 9.

South Korea's military claimed that the DPRK had already completed preparations for another atomic bomb test at its main Punggye-ri nuclear test site in northeastern DPRK where the country conducted all of its four nuclear detonations.

Ahead of the 7th WPK congress, the DPRK had test-fired several ballistic missiles to show its nuclear strike capability. Top DPRK leader Kim Jong Ungave orders on March 15 to test a nuclear warhead and ballistic rockets capable of carrying the warhead "in a short time."

Hong said the DPRK is ready to go its own way by firing long-range missiles at a time when the international society was discussing sanctions on Pyongyang over its fourth nuclear test.

The DPRK mentioned the need for inter-Korean talks, but the mentioning had no sincerity, Hong said. He called on Pyongyang to show its willingness for denuclearization first.