South Korea is closely monitoring the possibility of North Korea holding an event celebrating its 2017 launch of an intercontinental ballistic missile (ICBM), a unification ministry official said Thursday.

North Korea's calendars began to mark Nov. 29 as an anniversary for its "rocket" development this year. North Korean leader Kim Jong-un declared the completion of the country's nuclear force after firing the new ICBM, the Hwasong-15, on the day in 2017.

"We are keeping monitoring signs of celebratory events or related media reports as North Korean calendars began to mark the anniversary for the first time this year," the official told reporters on background.

The North's official media outlets have yet to report on the designation of the new anniversary.

"We will continue monitoring as there hasn't been any official explanation on the anniversary," the official added.

North Korea has been forging ahead with its nuclear and missile programs as seen in its tests earlier this year of new weapons, such as a new submarine-launched ballistic missile (SLBM) test in October. (Yonhap)