By Hyunsu Yim and Josh Smith

SEOUL (Reuters) -Russia's defence minister accompanied North Korean leader Kim Jong Un to a defence exhibition that featured the North's banned ballistic missiles as the neighbours pledged to boost ties, North Korean state media reported on Thursday.

The Russian minister, Sergei Shoigu, and a Chinese delegation including a Politburo member arrived in North Korea this week for the 70th anniversary of the end of the Korean War celebrated in North Korea as "Victory Day".

The missiles were banned under U.N. Security Council resolutions adopted with Russian and Chinese support but this week they provided a striking backdrop for a show of solidarity by three countries united by their rivalry with the U.S.

Shoigu is making the first visit by a Russian defence minister to North Korea since the fall of the Soviet Union.

For North Korea, the arrival of the Russian and Chinese delegations marks its first major opening up to the world since the coronavirus pandemic.

Shoigu gave Kim a letter from Russian President Vladimir Putin, North Korean media reported.

Kim thanked Putin for sending the military delegation led by Shoigu, saying the visit had deepened the "strategic and traditional" relations between North Korea and Russia.

"(Kim) expressed his views on the issues of mutual concern in the struggle to safeguard the sovereignty, development and interests of the two countries from the high-handed and arbitrary practices of the imperialists and to realize international justice and peace," North Korean media said.

"He repeatedly expressed belief that the Russian army and people would achieve big successes in the struggle for building a powerful country," it said.

KCNA did not refer to the war in Ukraine but North Korea's defence minister, Kang Sun Nam, was reported as saying North Korea fully supported Russia's "battle for justice" and to protect its sovereignty.

Kim led Shoigu on a tour of an exhibition of new weapons and military equipment, KCNA said.

State media photographs showed Kim and his guests at a display of some of the North's ballistic missiles in multi-axle transporter launchers. Another image showed what analysts said appeared to be a new drone.

One analyst said Shoigu's inspection of the North Korean missiles visit suggested Russian acceptance of North Korea's nuclear programme.

"We've come a long way from when North Korea would avoid showing off its nuclear capabilities when senior foreign dignitaries from Russia and China were in town," said Ankit Panda of the U.S.-based Carnegie Endowment for International Peace, calling the tour "remarkable".

"The personal tour for Shoigu - and Shoigu's willingness to be photographed with Kim in the course of this tour - is evidence that Moscow is complacent with North Korea's ongoing nuclear modernization," he said.

Kim also met Chinese Communist Party Politburo member Li Hongzhong for talks and was handed a letter from Chinese President Xi Jinping, North Korean media reported.

The visit by Li's delegation showed Xi's commitment to "attach great importance to the DPRK-China friendship," Kim was quoted as saying by the North's KCNA state news agency, referring to the North the initial of its official name, the Democratic People's Republic of Korea.

'NO SECRET'

The Russian visit raises the prospect of more open support for North Korea, especially with Russia isolated by the West over is invasion of Ukraine, analysts said.

"While Russia has kept its official military cooperation with the North Korea limited, any veritable rupture in the so-called post-Cold War order may see Russia more willing to openly violate sanctions, especially given their relatively lax attitude to the shifts in North Korea's nuclear status last year," said Anthony Rinna, a specialist in Korea-Russia relations at the Sino-NK think tank.

Last year, North Korea codified a new, expansive nuclear law declaring its status as a nuclear-armed state "irreversible".

This month, it threatened nuclear retaliation over a show of force by the United States, saying the deployment of strategic military assets near the Korean peninsula could meet criteria for its use of nuclear weapons.

White House national security spokesman John Kirby said Russia's overtures to North Korea comes as the Kremlin struggles to procure arms.

"It’s been no secret ... Mr Putin is reaching out to other countries for help and support in fighting his war in Ukraine. And that includes, we know, some outreach to the DPRK," he said.

North Korea has backed the Kremlin over its war with Ukraine and has shipped weapons including infantry rockets and missiles in support of Russia's war, the White House has said.

North Korea and Russia deny they have conducted arms transactions.

(Reporting by Hyunsu Yim, Hyonhee Shin, Ju-min Park, Josh Smith; Writing by Jack KimEditing by Ed Davies and Lincoln Feast)