Kim arrives in Russia for talks with Putin on first trip in four years

North Korean leader Kim Jong Un on Tuesday arrived in Russia on his first trip abroad in four years to attend a meeting with President Vladimir Putin that, according to the US, could see an arms deal to support Moscow's assault on Ukraine.

An unflappable Kim waved from the doors of his heavily armoured private train as it departed Pyongyang on Sunday evening, according to images published by Korean Central News Agency (KCNA).

Kim is set to meet with Putin, who is currently attending the Eastern Economic Forum in Vladivostok, in an unspecified location in Russia's Far East region later this week, according to Kremlin spokesman Dmitry Peskov.

However, there has been no indication that the internationally isolated pair would hold their talks there.

Experts predict Moscow will likely request artillery shells and antitank missiles from North Korea, seeking advanced satellite and nuclear-powered submarine technology in return.

Last week, the White House warned North Korea would "pay a price" if it supplies Russia with weaponry for the conflict in Ukraine.

Meanwhile, according to KCNA, Kim left North Korea for Russia on Sunday and was accompanied by top North Korean military officials, including officials in charge of weapons production and space technology.

Peskov said the two leaders would "cooperate on sensitive areas that should not be the subject of public disclosure and announcements".

On Tuesday, Russian news agency Ria Novosti said Kim had crossed the border, with images showing the train with dark green carriages being pulled along a track by a Russian Railways locomotive.