Those hurt in the bloody assault were taken by ambulance to hospitals in Donetsk, one of a dozen cities where pro-Kremlin separatists have taken over public buildings and reject Kiev's authority.
Several European journalists at the scene tweeted that they, too, were targeted by the pro-Russian group and had to run. They said Ukrainian riot police stood by and did nothing to stop the violence.
Russian state media reported the violence as a clash between pro-Russian "self defence groups" and pro-Kiev "ultra-nationalists".