The UN political affairs chief expressed willingness to ease tension on the Korean peninsula during a visit to North Korea this week, state media said on Saturday, amid a rising war of words over the North's missile and nuclear programmes.

North Korea also said in a statement carried by its official KCNA news agency that the UN envoy acknowledged the negative impact of sanctions on humanitarian aid to North Korea.

Jeffrey Feltman, the highest-level UN official to visit North Korea since 2012, did not speak to reporters upon arriving back from Pyongyang at Beijing airport on Saturday morning.

"The United Nations expressed concerns over the heightened situation on the Korean peninsula and expressed willingness to work on easing tensions on the Korean peninsula in accordance with the UN Charter which is based on international peace and security," KCNA said.

Speaking at an academic forum, Chinese Foreign Minister Wang Yi said the situation on the Korean peninsula had entered a vicious circle of shows of strength and confrontation, and the outlook was not optimistic, China's Foreign Ministry said in a statement.

"But at the same time it can be seen that hopes for peace have yet to extinguished. The prospects for negotiations still exist, and the option of resorting to force cannot be accepted," Wang was quoted as saying.　

North Korean leader Kim Jong Un gives field guidance to various units. Photo: KCNA via Reuters

North Korea is pursuing nuclear and missile weapons programmes in defiance of UN sanctions and international condemnation.

On November 29, it test-fired an intercontinental ballistic missile which it said was its most advanced yet, capable of reaching the mainland United States.

The United States and South Korea conducted large-scale military drills this week, which the North said have made the outbreak of war "an established fact".

KCNA said North Korean officials and Feltman agreed that his visit helped deepen understanding and that they agreed to communicate regularly.

Last month's missile test prompted a US warning that North Korea's leadership would be "utterly destroyed" if war were to break out. The Pentagon has mounted repeated shows of force after North Korean tests.

North Korea regularly threatens to destroy South Korea and the United States and says its weapons programmes are necessary to counter US aggression. The United States stations 28,500 troops in the South, a legacy of the 1950-53 Korean War.