Kim Jong Un has arrived in Russia for an expected meeting with President Vladimir Putin that has fueled Western concerns the North Korean leader will provide military support for Moscow’s war in Ukraine.

The South Korean defense ministry said Kim was believed to have entered Russia at dawn Tuesday local time, arriving on the luxury armored train on which North Korean leaders usually travel.

“We are closely monitoring if there will be negotiation between North Korea and Russia over the arms trade and technology transfer,” the ministry said in a briefing Tuesday, noting that Kim was accompanied by multiple military officers.

Russian news agency Interfax also confirmed that Kim was in Russia, citing Kremlin spokesperson Dmitry Peskov.