North Korean leader Kim Jong Un arrived in Russia on Tuesday ahead of a meeting with President Vladimir Putin that the United States has warned could see an arms deal to support Moscow's assault on Ukraine.

Making a rare foreign trip and his first since the pandemic, Kim was seen stepping onto a red-carpeted train platform before meeting Natural Resources Minister Alexander Kozlov.

Kim and Putin are expected to meet at an unspecified location in Russia's Far East later this week, the Kremlin has said.

Putin is currently attending the Eastern Economic Forum in Vladivostok, the Pacific port city closest to the North Korean border, though there has been no indication that the internationally isolated pair would hold their talks there.

Reporters granted access to the Russian leader at the forum refrained from asking Putin details of the visit but he told journalists he would soon travel to the Vostochny Cosmodrome, a Russian spaceport some 1,000 kilometres (620 miles) from Vladivostok.

"I've got my programme there, and when I get there you'll know," he was quoted by Russian news agencies as saying.

Kim received a VIP welcome from a military honor guard, with the national anthems of both countries playing, as he arrived in the Russian border town of Khasan Tuesday morning, the state-run KCNA news agency said.

Kim told his Russian hosts that his visit was a "clear manifestation" of North Korea "prioritizing the strategic importance" of its ties with Russia, KCNA said.

The agency did not specify when or where Kim would meet with Putin, saying only that after the arrival ceremony the North Korean leader "left for his destination."

Experts say Moscow will likely seek artillery shells and antitank missiles from North Korea, which wants advanced satellite and nuclear-powered submarine technology in return.

Siemon Wezeman, a senior researcher at the Stockholm International Peace Research Institute, said it was "entirely possible" North Korea had large stocks of ammunition that could be used by Russia.