LUHANSK, Ukraine — Timur, a 21-year-old student from Luhansk and a local activist with the EuroMaidan Revolution, is remarkably persistent. Until recently, he has consistently worn a blue-yellow ribbon, the colors of the Ukrainian flag.

But his patriotism causes him problems in eastern Ukraine, where Kremlin-backed separatism is strongest, especially in Donetsk and Luhansk oblasts, home to nearly 15 percent of Ukraine’s 45 million people.