North Korean leader Kim Jong Un appears to be on a train heading to Russia, multiple South Korean media outlets reported on Monday citing government officials, for a potential meeting with Russian President Vladimir Putin

Neither Russia nor North Korea have officially confirmed the meeting, but Putin reportedly arrived in the eastern Russian city of Vladivostok on Monday, Kremlin spokesman Dmitry Peskov said, according to state TV Russia 24.

The latest media reports come after US officials warned last week that Kim and Putin are expected to meet as arms negotiations advance between their two countries -- though no specific date or location as given for this potential meeting.

If the visit goes ahead it would mark Kim's first foreign trip since the Covid-19 pandemic. With its borders sealed because of that for much of the past three years, North Korea has only recently begun to relax travel restrictions.

It would also only be Kim's 10th trip since assuming power in 2011. All of those came in 2018 and 2019, as the North Korean leader engaged in negotiations over his nuclear weapons and missile programs in three meetings with then-US President Donald Trump -- one in Singapore, one in Hanoi and one in the demilitarized zone (DMZ) separating North and South Korea.

Kim also made four trips to China over those two years to meet with Chinese leader Xi Jinping, and he met once with Putin in Vladivostok in April 2019. The remaining trip was to the DMZ in 2018 to meet with then-South Korean President Moon Jae-in.

Vladivostok lies 130 km (80 miles) from the border with North Korea.

The North Korea leader is said to prefer traveling in an upscale armored train -- as did his father before him -- but rail travel accounts for less than half of his foreign trips. Three of this nine trips have been made in planes and two, both to the DMZ, by car.

Russian Defense Minister Sergei Shoigu also visited Pyongyang in July in an attempt to convince it to sell artillery ammunition.

Last Tuesday, White House national security adviser Jake Sullivan warned that North Korea it will "pay a price" if it strikes an arms deal with Russia, though he did not elaborate on these potential repercussions.

North Korea is already under United Nations and US sanctions imposed over Pyongyang's weapons of mass destruction program.

The potential Putin-Kim meeting could lead to Pyongyang getting its hands on the sort of weapons those sanctions have barred it from accessing for two decades, especially for its nuclear-capable ballistic missile program.

It also comes after more than a year and a half of war in Ukraine has left the Russian military battered, depleted and in need of supplies.