On a rare visit to North Korea, Chinese President Xi Jinping vowed to bring the complicated traditional alliance to "new heights", in a likely attempt to reassert Beijing’s unique influence over its neighbour as it moves closer to Moscow.

Upon arrival at Pyongyang's international airport on Monday, Xi and his wife Peng Liyuan were greeted by North Korean leader Kim Jong-un in a lavish welcome ceremony complete with a red-carpet military salute and cheering crowds, according to Chinese state media.

Some streets in the capital also displayed North Korean and Chinese flags side by side.

Xi later arrived at Pyongyang’s main square, where a military honour guard and thousands of people, including children carrying balloons and hopping, staged a welcoming ceremony.

Buildings surrounding the plaza were draped in the two countries’ flags, giant portraits of Kim and Xi and red-and-yellow banners welcoming the Chinese leader and celebrating the nations’ “friendship and unity.”