Censor.NET reports citing Poroshenko's Twitter.
"Fidel Castro passed away. We may not agree with his views, but his charisma has defined an entire epoch. Condolences to the people of Cuba," the president of Ukraine wrote.
"We will always remember the initiative of Fidel Castro, who felt deeply the pain of Chornobyl and helped to bring back to life thousands of little Ukrainians," Poroshenko said.
Castro's death was reported by Cuban state television on the night of Nov.26.