SEOUL - The Democratic People's Republic of Korea (DPRK) might be preparing for its fourth nuclear test, the Republic of Korea's unification minister said Monday.

"I can only say that there are such signs (of the DPRK's new nuke test)," Unification Minister Ryoo Kihl-jae told lawmakers at the parliamentary meeting for diplomacy and unification.

His comments came after a lawmaker said there is a rise in movements of personnel and vehicles near the test complex at Punggye-ri, North Hamgyong province, citing unspecified sources. The lawmaker asked whether the movement was the sign of the fourth nuke test.

The DPRK conducted its previous three nuke tests at the Punggye-ri test site. The latest occurred on February 12.

Ryoo noted that the question was related to "intelligence" things, declining to comment on details.

Asked about the possibility for Seoul to send a special envoy to Pyongyang, the minister said that "now is not the stage" to end the political deadlock through dialogue, noting that the special envoy "does not seem to guarantee easier tensions" on the Korean Peninsula.

His comments indicated that the ROK's government would not make a pre-emptive gesture for dialogue as the conciliatory gesture might send a wrong signal that Seoul caved in to Pyongyang's threats.

Minister Ryoo said that Seoul has had its door for dialogue with Pyongyang open, noting that Park Geun-hye government has never closed the door.

Regarding the entry ban to the Kaesong Industrial Complex, the minister said that 13 ROK's companies stopped factory operation until now at Kaesong due to lack of food and materials, forecasting that six more firms would halt their operations on Monday.

The DPRK has barred the entry of ROK's workers and vehicles to the inter-Korean industrial zone at the DPRK's border town of Kaesong for the sixth day, allowing only for their departure from Kaesong.

The industrial park, launched in late 2004, is housing 123 ROK's companies that are employing some 54,000 DPRK workers.