South Korea's military says it is keeping tabs for negotiations between North Korea and Russia over arms trade or transfer of military technology, which are in violation of United Nations Security Council(UNSC) sanctions on the regime.

Defense ministry spokesperson Jeon Ha-kyu said North Korean leader Kim Jong-un is believed to have entered Russia via train early Tuesday, accompanied by the military's top brass.

Asked whether the North Korean leader is expected to join Russian President Vladimir Putin at events aside from their bilateral meeting, the spokesperson said considering that the Eastern Economic Forum(EFF) is taking place the leaders could attend related events together.

Meanwhile, an official from Seoul's unification ministry said the two sides may also discuss a dispatch of North Korean laborers to Russia, referring to Kim being accompanied by Vice Premier Pak Hun, who reportedly oversees the North's construction sector.