A high-level delegation of Chinese officials will visit North Korea this week to attend celebrations for a key national holiday, both sides.

Pyongyang celebrates the 75th anniversary of the country's founding day on September 9 and the nuclear-armed state has previously indicated it will hold a "militia parade" to mark the event.

A delegation headed by China's vice premier Liu Guozhong "will visit the DPRK to participate in the celebrations of the 75th birthday," of the country, the official Korean Central News Agency said, using the country's official acronym.

The visit came "on the invitation" of North Korea's party and government, it added.

China's foreign ministry confirmed the trip, saying the delegation will visit North Korea "starting from September 8".

"We believe that with the joint efforts of both sides, this visit can be a complete success and promote the further deepening and development of China-DPRK ties," foreign ministry spokesperson Mao Ning said.

"China and North Korea are close neighbours connected by mountains and rivers, and the two parties and countries have always maintained a tradition of friendly communication."

Beijing is North Korea's most important ally and economic benefactor, their relationship forged in the bloodshed of the Korean War in the 1950s.

North Korea has been largely closed off from the outside world since early 2020, when it shut its borders in response to the Covid-19 pandemic.

But after three years of Covid-induced isolation, there are increasing signs Pyongyang may be becoming more flexible on border controls.

North Korea's first international commercial flight in three years landed in Beijing last month.

Pyongyang also allowed a delegation of athletes to attend a taekwondo competition in Kazakhstan in August.

The latest trip comes less than two months after high-level Chinese and Russian delegations visited Pyongyang.

They attended a military parade in the North Korean capital last month -- the first foreign dignitaries to visit the country in years.

The Chinese delegation was led by politburo member Li Hongzhong. During the parade, North Korean leader Kim Jong Un stood between Li and Russia's defence minister Sergei Shoigu, who was also visiting the country.

Kim gave Shoigu a tour of a vast defence expo in Pyongyang, personally walking him through his country's newest and most advanced weaponry.

There has been growing speculation that Kim -- who rarely leaves North Korea -- will meet with Russian President Vladimir Putin to discuss arms trade on the sidelines of a key forum in Vladivostok next week.