South Korea has been closely watching North Korea's movements related to the operations of its nuclear facilities, the defense ministry said Thursday, vowing to maintain a strong military posture against possible provocations by the North.

In protest against a fresh United Nations resolution condemning its grave human rights situation, Pyongyang threatened to intensify its nuclear weapons deterrence.

The website 38 North, run by the U.S.-Korea Institute at the Johns Hopkins School of Advanced International Studies, said Wednesday Pyongyang may be preparing to restart its reprocessing facility to extract weapons-grade plutonium from spent fuel, citing satellite imagery.

"The South Korean and the U.S. authorities have closely watched any movements by North Korea and operations of its nuclear facilities," defense ministry spokesman Kim Min-seok told a regular briefing.

The Joint Chiefs of Staff here declined to officially comment on its analysis of the North's recent nuclear activities, but an officer said on condition of anonymity that no specific moves have been detected at the North's Punggye-ri underground nuclear test site. 

Stressing that the best way for the North to prevent war is to give up its nuclear ambitions, the spokesman said the South Korean military "has maintained full preparedness, and we will not tolerate any provocations or threats by North Korea."

"Threats from North Korea could mean a nuclear test or a ballistic missile launch that would threaten peace not only on the Korean Peninsula but in the world, which should be completely deterred," Kim said.

The bellicose regime carried out three underground nuclear tests in 2006, 2009 and last year, and has threatened to perform "a new type" of nuclear test. (Yonhap)