Pyongyang will celebrate 70 years since the signing of the Korean War armistice on July 27, 1953, which ended open hostilities in the conflict and is known as Victory Day in the North, with state media saying it would be marked in a "grand manner that will go down in history".

Satellite imagery indicates the North has been preparing for the kind of large-scale military parade with which it typically fetes such anniversaries. But the inclusion of Chinese and Russian guests this year is a post-pandemic first, which hints at new flexibility towards enforcing border controls.

North Korea has been under a rigid self-imposed coronavirus blockade since early 2020 to protect itself from Covid-19, which has prevented even its own nationals from entering the country.

"A military delegation of the Russian Federation led by Defence Minister Sergei Shoigu will pay a congratulatory visit to the DPRK," the state-run Korean Central News Agency said, a day after it confirmed a Chinese delegation would also attend the Thursday event.

Shoigu in fact arrived in Pyongyang later Tuesday and was welcomed at the airport by his North Korean counterpart Kang Sun Nam, Shoigu's ministry said in Moscow.

Russia, a historic ally of Pyongyang, is one of a handful of nations that maintains friendly relations with the North.

Pyongyang's leader Kim Jong Un has been steadfast in his support for Moscow's invasion of Ukraine, including, Washington says, supplying rockets and missiles.

"This visit will contribute to strengthening Russian-North Korean military ties and will be an important step in the development of cooperation between the two countries," the Russian Defence Ministry said in a statement.

China also confirmed Tuesday it would send a delegation led by Politburo member Li Hongzhong.

- Seoul, Washington monitoring -

Seoul's defence ministry said Tuesday it had detected more "people and equipment" in the capital Pyongyang, adding that South Korean and US intelligence agencies were closely monitoring as the North prepared for the upcoming celebration.

The visits by the Chinese and Russian officials are the first known by any foreign delegation since the start of the pandemic.

The North only resumed some trade with China last year, and allowed Beijing's new envoy to take up his position this year.

Beijing said the delegation would travel to Pyongyang on Wednesday, suggesting they would not be required to undergo an extensive quarantine ahead of the Thursday anniversary event.

"After this event, North Korea is expected to ease its Covid restrictions while strengthening military cooperation with Moscow and Beijing," Cheong Seong-chang, director of the Center for North Korean Studies at the Sejong Institute, told AFP.

"Russia is expected to ask for more artillery support from North Korea to be used in the Ukraine war, and Pyongyang is also expected to ask for Russia's cooperation on reconnaissance satellites or nuclear submarines."

- US submarines -

North Korea tried -- but failed -- to launch its first military spy satellite in May, and has fired off multiple ballistic missiles recently to make clear its displeasure at Washington's deployment of a nuclear-capable submarine to the Korean peninsula.

The visit last week of the Ohio-class submarine was the first such deployment since 1981, and it was swiftly followed by the arrival of a second US submarine, the nuclear-powered USS Annapolis, at a South Korean naval base on Monday.

Relations between the two Koreas are currently at one of their lowest historical points, as diplomacy between Pyongyang and Seoul has stalled and Kim has called for ramping up weapons development, including tactical nukes.

In addition, a US soldier, Travis King, is currently believed to be in North Korean custody, after he ran across the border into North Korea during a tour of the demilitarised zone last week.