Russian President Vladimir Putin on Thursday announced a military operation in Donbas, which contains two separatist-held regions of Ukraine he declared independent this week. CNN reporters and witnesses in cities across Ukraine have reported hearing explosions in the early hours of Thursday. Ukraine"s President Volodymyr Zelensky made an appeal for peace to Russian citizens, saying they were not enemies — but that Kyiv would defend itself against any invasion. He said he had tried to call Putin on Wednesday but was unsuccessful. (Developing)