A paramilitary police officer stands guard in front of red flags at Tiananmen Square in Beijing, China.

Traditional friendship between China and North Korea represents "valuable wealth" for their people, China said after its special envoy met a high-ranking North Korean official, but there was no mention of the crisis over North Korea's weapons.

Song Tao, who heads the ruling Chinese Communist Party's international department, is visiting Pyongyang to discuss the outcome of the recently concluded Communist Party Congress in China, at which President Xi Jinping cemented his power.

In a brief statement dated Friday but reported by Chinese media on Saturday, the international department said Song, who is there representing Xi, reported to North Korean official Choe Ryong Hae the outcome of the congress.

Song and Choe also talked about relations between their parties and countries, the department said.

"They said that the traditional friendship between China and North Korea was founded and cultivated by both countries former old leaders, and is valuable wealth for the two peoples," it said.

"Both sides must work hard together to promote the further development of relations between the two parties and two countries to benefit their two peoples."

The department made no mention of North Korea's nuclear or missile programmes, which are strongly opposed by China.

The North's official KCNA news agency said Song informed Choe about China's 19th National Congress "in detail", and stressed China's stance to steadily develop the traditionally friendly relations between the two parties and countries.

Song arrived on Friday but it is not clear how long he will be in North Korea.

China has repeatedly pushed for a diplomatic solution to the crisis over North Korea's development of nuclear weapons and missiles to carry them, but in recent months it has had only limited high-level exchanges with North Korea.

The last time China's special envoy for North Korea visited the country was in February last year.