Xi turned to a topic Beijing has long pressed with its communist neighbour amid wider concerns over the North's nuclear weapons program.

In an address at a banquet on Thursday night, Xi noted that the nation under leader Kim Jong-un had "initiated a new strategic line of economic development and improving people's livelihoods, raising socialist construction in the country to a new high tide", according to China's official Xinhua News Agency.

Mr Xi left North Korea early on Friday afternoon, Chinese state media reported.

An image posted on the mobile app of state broadcaster CCTV showed people waving at his Air China 747 on the tarmac at the airport in Pyongyang.

The North's long-moribund economy has shown some recent improvements but it remains heavily dependent on aid - mainly from China - and food security is a constant concern.

China has agreed to UN economic sanctions over the North's nuclear and missile programs but is wary of any measures that could push its economy towards collapse, potentially unleashing instability and chaos on its border.

Xi's speech also touched on the nuclear issue, saying all sides agreed to "stick to peace talks so as to make even greater contributions to peace, stability and prosperity in the region and the wider world", Xinhua said.

North Korean state media said Xi and Kim held broad discussions over the political situation surrounding the Korean Peninsula and reached a shared understanding on the issues they discussed.

The Korean Central News Agency report did not give any specifics on the stalled nuclear negotiations between Washington and Pyongyang over disagreements in exchanging sanctions relief for disarmament.

"The supreme leaders... broadly exchanged their opinions on the political situation of the Korean Peninsula and other serious international and regional issues," KCNA said.

Australian Associated Press