Hundreds of pro-Russian militiamen and sympathizers attacked Odessa police headquarters Sunday and attemptedto capture it, in revenge for the deaths of some 50 supporters Saturday in a fire set by pro-Kiev militants at the Odessa trade union building. Dozens of people trapped in the building were burned alive or choked to death, and at least eight jumped to their death from high windows.  DEBKAfile’s military sources report that the transitional government in Kiev, which launched its first major military offensive Friday against the pro-Russian revolt in the east, is hard put to wield its forces effectively. Their numbers are too small to overpower the 10 million ethnic Russians of the eastern provinces and the militias they have set up to promote their separatist agenda.