Multiple media outlets in South Korea report that North Korean Leader Kim Jong Un is likely on his way to Russia.
Yonhap News Agency quoted government sources as saying intelligence authorities believe a train presumed to be carrying Kim is traveling to the Russian Far Eastern city of Vladivostok.
Major newspaper Dong-A Ilbo also says the train will likely cross the border into Russia as early as Tuesday morning.
Russia's state-run news agency says President Vladimir Putin also arrived in Vladivostok on Monday. They will likely hold a summit. But neither Russia nor North Korea have made a formal announcement so far.
It would be Kim's second visit to Russia -- and his first in four years.
Meanwhile, police officers were seen standing guard in Vladivostok's central district on Monday. The Kremlin said Putin will be in the city for two days. It's unclear when and where the expected summit with Kim will take place.