At least five explosions were heard in the separatist-held eastern Ukraine city of Donetsk early on Thursday, a Reuters witness said.
Following the blasts, four military trucks could be seen heading for the scene. Hours earlier, the Kremlin said two separatist breakaway regions in Ukraine had asked for Russian help to repel "aggression" by the Ukrainian army.
(Reporting by a Reuters reporter in Donetsk; Writing by David Ljunggren; Editing by Jacqueline Wong)
