North Korea could opt to carry out another nuclear test ahead of the country's rare ruling party congress set for later this week as it has completed all preparations at its Punggye-ri test site, the defense ministry said Tuesday.

North Korea appears to be "plotting further strategic provocations including a nuclear test, the test-firing of a Musudan intermediate range missile and another submarine-launched ballistic missile launch," the Ministry of National Defense said in a parliamentary report released to the media.

The government has repeatedly warned of North Korea's possible nuclear test and other adventurist military provocations as the country is set to open the first congress of the Workers' Party of Korea in more than 30 years.

"The Punggye-ri nuclear test site is in a condition to carry out the nuclear test at any time," the ministry said. "There is a possibility of an additional nuclear test in a bid to showcase leader Kim Jung-un's accomplishments before the party congress."

The North may set the date to implement such provocations after weighing the intensity of sanctions it is facing, as well as the political mood in and outside the country, the ministry added.

North Korea also appears to be "obsessed" with ballistic missile development as the country is trying to save face following its recent botched launches of Musudan missiles and its SLBM, which have been reported by the South Korean media, the ministry said.

Defense Minister Han Min-koo assured lawmakers that Seoul possesses credible deterrent against a possible N. Korean nuclear test. He vowed to counter North Korea's provocations by joining hands with Seoul's allies.

"(South Korea) has firm deterrence against (N. Korea's nuke test)," Han said in a parliamentary defense committee hearing, saying that our military will mobilize not only its own capabilities but also work closely with allies. 

Sources said North Korea has recently put its frontline troops on special readiness alert, a possible sign of imminent military provocations.

"North Korea has lately ordered its border regions to maintain a special readiness posture," one government source said. "Our military concluded that it could be a sign of the country planning some sort of provocation around the time the Workers' Party of Korea congress is going to be held."

In response, the South Korea and United States alliance has intensified its surveillance of the North, the sources said.

They also indicated that the communist country has also restricted North Korean boats' fishing activities in certain parts of the East and Yellow Seas which could mean the country may be readying for a missile launch into these waters in the near future. (Yonhap)