SEOUL -- No imminent signs were detected yet on the Democratic People's Republic of Korea (DPRK)'s another nuclear test though Pyongyang seemed to be prepared to conduct its fourth nuclear test at any time, Yonhap News Agency reported Friday citing Seoul's Defense Ministry.

Vice Defense Minister Baek Seung-joo made such reports to lawmakers of the ruling Sanuri Party at the special meeting for security strategy on the DPRK's nuclear program, according to participants of the meeting cited by Yonhap.

Baek said that the southern tunnel of the underground test site in the DPRK's northeastern region of Punggye-ri can be used for another nuclear test at any time, but adding that no signals have been found that the test is imminent.

The western tunnel, where the third nuclear test was conducted in February, was being renovated, Baek said.

His comments came amid rising speculation over Pyongyang's fourth nuclear test. A US institute estimated that the DPRK has prepared for another nuclear test at its main Punggye-ri test site, citing recent satellite photos. ?

"Recent commercial satellite imagery has identified two new tunnel entrances and continued excavation at the Punggye-ri nuclear test site,"the US-Korea institute at Johns Hopkins School of Advanced International Studies (SAIS) said in an Oct 23 report posted on its website "38 North".

The western tunnel may have been continuously excavated, according to the Sept 27 satellite images secured by the SAIS. Digging of the tunnel may have begun when spoil was first spotted in mid-May and continued through late September, the institute said.

New imagery also showed what may be a second tunnel under construction off the main road in the southern tunnel area of the test site.