North Korean leader Kim Jong-un may visit one of his country's closest remaining allies, China, in the near future, a top Chinese diplomat has said.

Beijing's ambassador to South Korea, Qiu Guohong, was speaking during a conference when he said a visit by North's leader may be on the cards.

"I think that a visit by North Korean leader Kim Jong-un to China is likely to be made down the road," South Korea's Yonhap news agency reported Qiu as saying.

The 30-something Kim took over as North's leader following his father Kim Jong-Il's death in 2011. The new leader has not made any foreign trip since then just like his father Kim, who made his overseas tour to China only after six years of consolidating his control in the country.

"China and North Korea have maintained a normal relationship and there have been normal exchanges of visits between the leaders of both countries. I don't think that should be closely tied to the question of whether China-North Korea relations are good or bad," added Qiu in his address.

China remains a staunch ally of North Korea despite efforts by western nations to further isolate the country over Pyongyang's contentious nuclear programme.

China's border with North Korea is relatively unguarded compared to its other borders with South Korea and Russia.

However, relations between the two countries have been turning sour at times, especially after Xi Jinping became the Chinese president. Xi visited South, North's arch-rival, but failed to visit Pyongyang recently. Xi's South visit was widely interpreted as a direct snub to North in China's attempt to distance itself from its troublesome neighbour.