South Korea's unification ministry said Monday that North Korea is ready to conduct a nuclear test at any time as Pyongyang's provocation would hinge on its internal plan for nuclear weapons development.

Satellite imagery of the North's nuclear test site in the northeast area shows that a tunnel under continued excavation has displayed potential for North Korea to carry out an additional nuke test of significantly higher explosive yields, according to 38 North, a US website monitoring the North.

The ministry said that it sees North Korea being able to conduct a nuclear test at any time if its leadership makes the order to do so.

"The government believes that Pyongyang can carry out a nuclear provocation at any time as its nuke test is carried out in accordance with the country's plan on nuclear weapons development," Jeong Joon-hee, ministry spokesman, said at a regular press briefing.

North Korea conducted two nuclear tests last year alone following those in 2006, 2009 and 2013.

Pyongyang is seeking to conduct another nuclear test around South Korea's presidential election this year, Thae Yong-ho, a former North Korean diplomat who defected to Seoul last year, told lawmakers in December.

Experts said that the North may stage a missile or nuclear provocation in April when the country marks key anniversaries.

The North will celebrate the 105th birthday of the country's late founder Kim Il-sung, which falls on April 15. The Korean People's Army marks the 85th anniversary of its creation on April 25.

Meanwhile, the ministry rejected North Korea's repeated claim that it does not need to possess nuclear weapons if Seoul and Washington stop their annual military drills.

South Korea and the United States kicked off their military exercises on March 1 amid heightened tensions following the North's launch of a new intermediate-range ballistic missile in February.

North Korea has denounced the drills as war rehearsals for a northern invasion despite Seoul and Washington's assurance that they are defensive in nature.

Jeong said that the North's claim that it would abandon its nuclear weapons program in exchange for the end of the military drills has been proven wrong. (Yonhap)