North Korean leader Kim Jong Un has accepted Russia’s invitation to attend an anniversary event in Moscow in May, marking the Soviet’s victory over Germany in World War II, South Korea's Yonhap news agency reported Wednesday, citing Kremlin officials.

According to the report, the Kremlin has said that world leaders of about 20 nations have confirmed their plans to attend the event, and the North Korean leader is among them. Russia’s Foreign Minister Sergey Lavrov said last week that Kim Jong Un is expected to accept the Kremlin’s invitation to visit Russia in May. If Kim Jong Un makes the trip, this will be his first foreign visit since taking power from his late father, Kim Jong Il, in 2011. The Moscow tour is likely to come before the North Korean leader visits China, the North's main ally.

However, in a written response, the Kremlin did not mention Kim Jong Un’s name, the Yonhap report said, adding that South Korean officials believe Pyongyang could send Kim Yong Nam, the state's nominal head and chairman of the Presidium of the Supreme People's Assembly of North Korea, to Russia.

“When you refer to North Korea's leader, it's ambiguous at times. Under the North's Constitution, Kim Yong-nam represents the country in external relations,” Yonhap quoted a unification ministry official of South Korea, as saying. 

North Korea and Russia have been trying to boost their ties over the last few months. In November, Russian President Vladimir Putin called on deeper cooperation with North Korea to improve regional security. Putin also held talks with a personal envoy of Kim Jong Un at the time, but details of the meeting were not made public.

“We maintain friendly relations with one of our neighbors, the Democratic People's Republic of Korea,” Putin said at the time. “A further deepening of political ties and trade and economic cooperation is definitely in the interests of the peoples of both countries and ensuring regional stability and security.”

While Moscow and Pyongyang are exploring ways to improve their bonding, North Korea’s ties with China have weakened since Kim Jong Un came to power. The relations cooled further in 2013 when North Korea disregarded international warnings and U.N. sanctions to conduct a third nuclear test, Reuters reported.