North Korean leader Kim Jong-un visited the mausoleum of his late grandfather and father in his first reported public activity this year, according to Pyongyang's state media Monday.

Kim paid tribute at the Kumsusan Palace of the Sun, where the bodies of state founder and his grandfather, Kim Il-sung, and his father, Kim Jong-il, are enshrined, on the occasion of the start of the new year, the Korean Central News Agency said.

The visit to the mausoleum came after he unveiled this year's policy direction and called for an "exponential" increase in the country's nuclear arsenal during a rare six-day meeting of the ruling Workers' Party held until Saturday.

Top officials accompanied Kim on his visit to the mausoleum, including Premier Kim Tok-hun and Jo Yong-won, the party secretary for organizational affairs.

Separately, Kim also held a photo session with the participants in the 9th Congress of the Korean Children's Union that opened last week in Pyongyang for the first time in five years, according to the KCNA.

The KCU, formed in 1946, is a youth organization composed of children aged around 7 to 13. Its members are known for wearing red neckerchiefs. (Yonhap)