Pro-Russian militants in eastern Ukraine vowed on Thursday to press ahead with a referendum seeking autonomy, a risky move that seemed to defy their political patron, President Vladimir V. Putin of Russia, whose motives in urging a delay in the vote came under furious attack by officials in Kiev. A day after Mr. Putin scrambled the political landscape by suggesting the vote be put off, militant leaders in Donetsk, Luhansk and Slovyansk said they would go ahead on Sunday as scheduled. Far from mollified by Mr. Putin’s new stance, Ukrainian officials expressed deep suspicions, accusing him of trying to replay events preceding Russia’s annexation of Crimea. Although the ability of separatists to stage a legitimate ballot is highly in doubt, the mere possibility that Russia would use the vote as a pretext for another territorial grab had officials in Kiev calling the referendum illegal and insisting that action […]