North Korean leader Kim Jong Un's train has entered Russia and is moving north along the coast toward the Amur region after stopping at Khasan station, sources close to Russian authorities said Tuesday.

Russian President Vladimir Putin told the Eastern Economic Forum being held in Vladivostok the same day that he "has a plan" at the Vostochny Cosmodrome space launch center in the region, indicating a meeting with Kim is likely to take place Wednesday.

The sources said Kim will visit a factory that manufactures Sukhoi fighters and other aircraft in Komsomolsk-on-Amur in the Russian Far East, following his talks with Putin.

According to the data from the Flightradar24 website, an Air Koryo airplane, which is believed to be the one used by Kim for domestic trips, took off from Pyongyang International Airport on Tuesday morning and arrived in Vladivostok, indicating North Korean officials who would assist Kim might have been on board.

The official Korean Central News Agency said the same day that Kim had departed from Pyongyang for Russia, following its earlier report that he will meet with Putin during the trip.

North Korean leader Kim Jong Un waves as he boards his train in Pyongyang on Sept. 10, 2023, to visit Russia. (KCNA/Kyodo) 

The United States said last month that Russia was stepping up efforts to reach an agreement for North Korea to provide military assistance for Moscow's war in Ukraine.

Kim left the North Korean capital on Sunday accompanied by leading officials of the ruling Workers' Party of Korea, the government and armed forces, the latest KCNA report said.

The report did not specify Kim's destination. Russia's Tass news agency said Putin arrived Monday in Vladivostok, where the Eastern Economic Forum is being held.

The two leaders are expected to confirm their countries' close ties, following the agreement on enhanced defense cooperation reached by the United States, Japan and South Korea at a trilateral summit last month.

U.S. State Department spokesman Matthew Miller told reporters Monday that any arms transfers from North Korea to Russia would violate U.N. Security Council resolutions, warning that the United States will not hesitate to impose additional sanctions on the two countries.

The two leaders last met in April 2019 in Vladivostok and the current trip is the first time Kim is known to have left North Korea since, as the nation closed its borders due to the novel coronavirus pandemic.

Kim last held a summit with a foreign leader in June 2019, when he met with then U.S. President Donald Trump in the inter-Korean truce village of Panmunjeom.

In this photo taken from a video released by telegram channel @primamedia on Sept. 12, 2023, a green train with yellow trimmings, resembling one used by North Korean leader Kim Jong Un on his previous travels, is seen steaming near Khasan in the Russian Far East. (telegram channel @primamedia/AP/Kyodo)

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