North Korean leader Kim Jong Un arrives in Russia before meeting with Putin

Joined by his top military officials handling his nuclear-capable weapons and munitions factories, North Korean leader Kim Jong Un arrived in Russia on Tuesday, where he is expected to hold a rare meeting with President Vladimir Putin that has sparked Western concerns about a potential arms deal for Moscow's war in Ukraine.

North Korea's official news agency said Kim boarded his personal train from the capital, Pyongyang, on Sunday afternoon, and that he was accompanied by unspecified members of the country's ruling party, government and military.

Jeon Ha Gyu, spokesperson of South Korea's Defence Ministry, said in a briefing that the South's military assesses that Kim's train crossed into Russia sometime early Tuesday. He didn't elaborate how the military obtained the information.

North Korean state media showed photographs of Kim walking past honour guards and crowds of civilians holding the national flag and flowers, and also of him waving from his green-and-yellow armoured train before it left the station.

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

Citing unidentified Russian regional officials, Japanese broadcaster TBS reported that Kim's train crossed the border and arrived in the border town of Khasan.

A brief statement on the Kremlin's website on Monday said the visit is at Putin's invitation and would take place in the coming days. KCNA said the leaders would meet without specifying when and where.

Kremlin spokesperson Dmitry Peskov said that Putin and Kim will lead their delegations in talks and could also meet one-on-one if necessary. He added that Putin will host an official dinner for Kim.

The talks will focus on bilateral ties, Peskov said. As with any of our neighbours, we feel obliged to develop good, mutually beneficial relations, he added.

A possible venue is 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. The city, located about 425 miles (680 kilometers) north of Pyongyang, was also the site of Putin's first meeting with Kim in 2019.

The visit would be Kim's first foreign trip since the COVID-19 pandemic, which had forced North Korea to enforce tight border controls for more than three years to shield its poor health care system. While Kim has shown to be more comfortable using planes than his famously flight-adverse father, he has also used his personal train for previous meetings with Putin, Chinese President Xi Jinping and former US President Donald Trump, reviving a symbol of his family's dynastic rule.