North Korean leader Kim Jong Un has crossed over into Russia ahead of a meeting with President Vladimir Putin. Their aides have not provided many details, fueling Western concerns about military cooperation. Russian officials, however, say the two leaders will reach a new security agreement.

Kim is traveling on his armored train, making a slow journey to his first meeting with Putin in four years. It has not been announced where or when they will sit down together.

Russian officials told NHK that the two will come up with a framework for cooperating on military technology. They will also discuss support for building nuclear plants in North Korea.

Putin has been looking for new suppliers of weapons to help the war in Ukraine in the face of Western sanctions imposed after the invasion.

Western analysts are trying to figure out where Kim is traveling to. They believe his train passed by Vladivostok. And railway officials say the train is headed north to the Amur region.

Putin has confirmed he will visit a space center called Vostochny Cosmodrome in the area. However, he did not say he would host Kim there, adding that people will know once he gets there.