North Korean leader Kim Jong Un visited a Russian military aviation factory on Friday following his summit with president Vladimir Putin, as the two countries ostracised by the West seek deeper ties.

Historic allies, Russia and North Korea are both under rafts of global sanctions -- Moscow for its Ukraine conflict, Pyongyang for its nuclear tests -- with Kim's rare foreign visit sparking concern from Kyiv's allies over a possible arms deal.

Putin, who has sought to strengthen alliances with other leaders shunned in Western capitals, met Kim on Wednesday at a spaceport in Russia's far east.

While Pyongyang wants Moscow's help to develop its missile programme, US officials and experts have said Russia is interested in buying North Korean ammunition to use in Ukraine.

After their summit at the Vostochny cosmodrome, Putin told reporters that he saw "possibilities" for military cooperation.

On Friday, Kim visited military and civil aviation plants in far eastern Komsomolsk-on-Amur, a key Russian engineering hub, Moscow said in a statement.

Kim saw the production of Russia's Sukhoi Su-35 and Su-57 fighter aircraft and watched a Su-35 demonstration flight, the statement said.

"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," the trade and industry minister said.

Western countries have warned Moscow and Pyongyang against making an arms deal that would defy global sanctions.

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.

Kim's far east visit will last a few more days, Kremlin spokesman Dmitry Peskov said Thursday.

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.

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."

Russia is facing unprecedented isolation from the West over Moscow's Ukraine offensive, with Putin seeking to boost Soviet-era alliances.

US consults Tokyo, Seoul

The Kremlin confirmed Thursday 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," said Matsuno.

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," Yonhap news agency quoted him as saying.

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