North Korea's Kim Jong-un arrives in Russia for talks with Putin as 2 ...

North Korea's Kim Jong-un arrived in Russia on Tuesday for a meeting with President Vladimir Putin where they are expected to offer each other increased support in their escalating standoffs with the West.

Kim is expected to seek Russian economic aid and military technology in exchange for munitions to be used in Russia's war in Ukraine.

North Korea's official Korean Central News Agency said Kim boarded his personal train bound for Russia on Sunday afternoon, accompanied by members of the ruling party, government and military.

After decades of complicated, hot-and-cold relations, Russia and North Korea have drawn closer since Moscow's invasion of Ukraine in 2022. The bond has been driven by Putin's need for war supplies and Kim's efforts to boost his partnerships with traditional allies Moscow and Beijing as he tries to break out of diplomatic isolation.

South Korea's military assessed the train crossed into Russia early Tuesday, Jeon Ha Gyu, spokesperson of South Korea's Defence Ministry, said without elaborating on how the military obtained the information.

Kremlin spokesperson Dmitry Peskov confirmed only that Kim has entered Russia, and state news agency RIA-Novosti later reported his train had headed north after crossing the Razdolnaya River, taking it away from Vladivostok, where Putin was participating in a dayslong economic forum.

Peskov said Putin and Kim will meet after the Vladivostok forum, and that the meeting would include a lunch in Kim's honour.

Kim is apparently accompanied by Jo Chun Ryong, a ruling party official in charge of munitions policies who joined the leader on recent tours of factories producing artillery shells and missiles, said South Korea's Unification Ministry.

North Korea may have tens of millions of artillery shells and rockets based on Soviet designs that could give a huge boost to the Russian army in Ukraine, analysts say.

"The burn rate of everything, particularly artillery, is very high [in the war]," Andrew Rasiulis, a fellow with the Canadian Global Affairs Institute, told CBC News on Monday. "The Russians could certainly benefit from more ammunition from North Korea, and North Korea has exactly the calibre of ammunition because of the old Soviet base for the equipment they use."

Speculation about military co-operation grew after Russian Defence Minister Sergei Shoigu visited North Korea in July, when Kim invited him to an arms exhibition and a massive military parade in the capital showcasing intercontinental ballistice missiles designed to target the U.S. mainland. Following that visit, Kim toured North Korea's weapons factories, including a facility producing artillery systems, urging workers to speed up development and large-scale production of new kinds of ammunition.

Also identified in photos from North Korean state media were Pak Thae Song, chairman of North Korea's space science and technology committee, and Navy Adm. Kim Myong Sik, who are linked with North Korean efforts to acquire spy satellites and nuclear-capable ballistic missile submarines. Experts say North Korea would struggle to acquire such capabilities without external help, although it's not clear if Russia would share such sensitive technologies.

Kim, making his first foreign trip since the pandemic arrived, may also seek badly needed energy and food supplies, analysts say. Deputy foreign minister Andrei Rudenko said Russia may discuss humanitarian aid with the North Korean delegation, according to Russian news agencies.

Lim Soo-suk, South Korea's Foreign Ministry spokesperson, said Seoul was maintaining communication with Moscow while closely monitoring Kim's visit.

"No UN member state should violate Security Council sanctions against North Korea by engaging in an illegal trade of arms, and must certainly not engage in military cooperation with North Korea that undermines the peace and stability of the international community," Lim said during a briefing.

Russia has supported those sanctions in the past.

Moscow seeks to rebuff a Ukrainian counteroffensive and show that it's capable of grinding out a long war of attrition. Sustained North Korean support could potentially put more pressure on the U.S. and its partners to pursue negotiations as concerns over a protracted conflict grow despite their huge shipments of advanced weaponry to Ukraine in the past 17 months.

"We urge the DPRK to abide by the public commitments that Pyongyang has made to not provide or sell arms to Russia," said White House National Security Council spokesperson Adrienne Watson, using the abbreviation for North Korea's official name of the Democratic People's Republic of Korea.

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Raisulis told CBC News that Washington has a right to be concerned, but that their options are somewhat limited if the two countries draw closer in terms of military co-operation.

"The Americans have said that they would probably increase sanctions on North Korea, but at the same time, North Korea is heavily sanctioned as it is, so to say you're going to do more of that stuff, I'm not sure how much of an impact it has politically on the motivations of the North Korean political leadership," he said.

The United States has accused North Korea of providing Russia with arms, including selling artillery shells to the Russian mercenary group Wagner. Both Russian and North Korean officials denied such claims.