Kim Jong Un says visit to China is his 'solemn duty'

North Korea's Kim Jong Un told Chinese President Xi Jinping that it was his "solemn duty" to make Beijing his first overseas destination as he made his maiden foreign trip as leader, Pyongyang's official news agency reported Wednesday.

The relationship between the North and its key protector has soured in recent years, with China increasingly exasperated by its neighbour's nuclear antics, and recently showed a new willingness to enforce United Nations sanctions imposed on it over its weapons and missiles programmes.

But KCNA quoted Kim saying at a banquet in Beijing: "There is no question that my first foreign visit is to the Chinese capital.

"This is my solemn duty as someone who should value and continue the DPRK-PRC relations through generations," he added using the countries' official acronyms.

KCNA described the visit as unofficial and said it ran from Sunday to Wednesday, implying that Kim's armoured train entered China at the weekend and crossed back into North Korea early Wednesday after leaving Beijing on Tuesday afternoon.

Kim was accompanied by his wife Ri Sol Ju and several officials and dignitaries, KCNA said, without mentioning his sister Kim Yo Jong, who acted as his special envoy to last month's Winter Olympics in the South, which has triggered an unprecedented flurry of diplomatic activity on and around the flashpoint peninsula.