North Korean leader Kim Jong Un arrived in Russia on Tuesday for an expected meeting with President Vladimir Putin that has sparked concerns about a potential arms deal for Moscow’s war in Ukraine, joined by top military officials in charge of nuclear-capable weapons and munitions factories.

North Korea’s official Korean Central News Agency said Kim boarded his personal train Sunday afternoon, accompanied by unspecified members of the country’s ruling party, government and military.

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

Officials identified in North Korean state media photos may hint at what Kim might seek from Putin and what he would be willing to give.

Kim Jong Un is apparently bringing Jo Chun Ryong, a ruling party official in charge of munitions policies who accompanied 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.

Also identified in photos 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 may also seek badly needed energy and food aid, analysts say.

Kim’s delegation likely includes his foreign minister, Choe Sun Hui, and his top two military officials, Korean People’s Army Marshals Ri Pyong Chol and Pak Jong Chon.

Kim and Putin may meet in the eastern Russian city of Vladivostok, where Putin arrived Monday to attend an international forum that runs through Wednesday, according to Russia’s TASS news agency. Putin’s first meeting with Kim was held in 2019 in the city, which is about 425 miles (680 kilometers) north of Pyongyang.

Russian news agencies quoted Kremlin spokesperson Dmitry Peskov as saying Putin and Kim will meet after the Vladivostok forum, but the reports didn't specify when or where.

Peskov said the meeting would include a lunch in Kim’s honor.

Deputy foreign minister Andrei Rudenko said that Russia will inform South Korea about the meeting's outcome upon request: “The South Koreans have an embassy in Moscow. If they want, we can provide them with the information we have.”

Kim Jong Un is making his first foreign trip since the Covid-19 pandemic, during which North Korea imposed tight border controls for more than three years.