Seoul says North Korea capable of another nuclear test

South Korean shout slogans during a rally denouncing North Korea's latest nuclear test in Seoul, South Korea, Monday, Sept. 12, 2016. North Korea is capable of detonating another nuclear device anytime at one of its unused tunnels at the country's main atomic test site, Seoul official said Monday, three days after the country carried out its fifth bomb explosion. The letters read "Overthrow Kim Jong Un." (AP Photo/Lee Jin-man) (The Associated Press)

A South Korean army's K1 tank moves during an annual exercise in Paju, South Korea, near the border with North Korea, Sunday, Sept. 11, 2016. The U.N. Security Council is strongly condemning North Korea's latest nuclear test and says it will start discussions on "significant measures" against Pyongyang including new sanctions. (AP Photo/Ahn Young-joon) (The Associated Press)

A South Korean official says North Korea is capable of conducting another nuclear test anytime at one of its unused tunnels at the country's main atomic test site.

The comments by Defense Ministry spokesman Moon Sang Gyun on Monday came three days after North Korea carried out its fifth atomic bomb test.

Moon refused to say what evidence pointed to another possible North Korea test, but said South Korea and U.S. intelligence authorities believe North Korea has the ability to detonate another atomic device anytime.

South Korea's Yonhap news agency, citing unidentified Seoul government sources, reported Monday that there is evidence showing the North has finished new test preparations at one previously unused tunnel in the Punggy-ri test site.

Yonhap didn't say how the sources got the information.