The Kremlin said Friday that no agreements had been signed during North Korean leader Kim Jong Un's ongoing visit to Russia, amid Western concern that the two isolated countries could be preparing an arms deal.

Kim is on a rare trip out of his reclusive country in the Russian Far East, where he met with Russian President Vladimir Putin earlier this week.

Moscow is believed to be interested in buying North Korean ammunition to continue fighting in Ukraine, while Pyongyang wants Russia's help to develop its missile programme.

Western countries have warned Russia and North Korea against striking an arms deal, which would defy sanctions on Pyongyang.

"No agreements were signed and there was no plan to sign any," Kremlin spokesman Dmitry Peskov told reporters.

After meeting Kim on Wednesday, Putin said he saw "possibilities" for military cooperation.

As part of his extended tour of the Russian Far East, Kim visited a Russian military aviation factory Friday in Komsomolsk-on-Amur, a key Russian engineering hub, Moscow said.

He saw the production of Russia's Sukhoi Su-35 and Su-57 fighter aircraft and watched a demonstration flight of an Su-35.

"We see the potential for cooperation both in the field of aircraft manufacturing and in other industries," said Russian Deputy Prime Minister Denis Manturov after accompanying Kim around the factories.

"This is especially important for achieving the tasks facing our countries to achieve technological sovereignty," said Manturov, also the trade and industry minister.

Russia has said that Kim will continue his visit for several more days, without giving a specific time frame.

- Bullet-proof train tour -

Kim is visiting Russia in his bullet-proof train on his first official trip abroad since the Covid-19 pandemic broke out. He left Pyongyang on Sunday and crossed their shared border on Tuesday.

Putin said Wednesday that Kim would visit the port of Vladivostok to see the capabilities of Russia's Pacific Fleet.

Kim is accompanied by a military-heavy entourage, while top Russian military officials were also involved in the Putin talks.

Moscow's and Pyongyang's ties are rooted in the Soviet Union's role in the founding of North Korea.

During Kim's visit, Putin and Russian officials have heavily referenced the 20th century to call for a stronger relationship today, when Moscow is facing unprecedented isolation over its Ukraine offensive.

Khabarovsk regional governor Mikhail Degtyarev, who joined Kim on the jet factory visit, said afterwards on Telegram: "Today we stand together against the pressure of the collective West.

"Through joint efforts, both states will continue to defend the ideals of freedom and a multipolar world."

- US consults Tokyo, Seoul -

On Thursday, the Kremlin confirmed that Putin had accepted Kim's invitation to visit North Korea.

It would be Putin's second trip to the country: He met Kim Jong Il in Pyongyang in July 2000, shortly after becoming Russia's president.

The White House said Thursday that US National Security Advisor Jake Sullivan had spoken with his Japanese and South Korean counterparts to discuss the Putin-Kim meeting.

They noted that any arms exports from North Korea to Russia "would directly violate multiple UN Security Council resolutions, including resolutions that Russia itself voted to adopt", a White House statement said.

A top Japanese government official said Friday that Prime Minister Fumio Kishida was willing to meet Kim "without pre-conditions".

Kishida had previously said he was ready to hold talks with Kim, but the repeated invitation comes as regional concerns around the Putin talks grow.

"We would like to hold high-level discussions under direct control of the prime minister to achieve a summit meeting as soon as possible," Japan's Chief Cabinet Secretary Hirokazu Matsuno told reporters.

Kishida "has been expressing his determination to directly face" Kim at "any time and without pre-conditions", Matsuno said.

South Korean Foreign Minister Park Jin said Friday that Seoul was considering further sanctions against Moscow and Pyongyang if they strike an arms deal.

"If North Korea reaches any agreement regarding arms trade through a summit with Russia, it would be an act that seriously threatens peace and security on the Korean peninsula," the Yonhap news agency quoted him as saying.

Asked about potential additional sanctions, he added: "We are considering all possible options."