A Russian defense official Sunday said trains carrying the remains of Ukrainian soldiers would be dispatched to an area near the Ukrainian border, stepping up tensions between Moscow and Kyiv over a long simmer dispute over a war prisoner swap.

Ukrainian President Volodymyr Zelenskyy said he would press on with plans for a prisoner swap with Moscow, although he expressed doubts about a successful outcome, while his military leaders denied Russian claims that its forces had for the first time advanced into the eastern Dnipropetrovsk region.