By Marek Strzelecki, Tsvetelia Tsolova and Pavel Polityuk WARSAW/SOFIA/KYIV (Reuters) -Russia halted gas supplies to Bulgaria and Poland on Wednesday for rejecting its demand for payment in roubles, taking direct aim at European economies in a move that also exposed divisions in the EU on how to respond to Moscow’s invasion of Ukraine. The decision, denounced by European leaders as “blackmail”, comes as Russia’s own economy wilts under sweeping international sanctions and as Western countries ramp up arms shipments to help Ukraine fend off a new Russian assault in the east. Ukraine reported on…