ROSTOV-ON-DON/VORONEZH, Russia, June 24 (Reuters) – Russian military helicopters opened fire on Saturday afternoon on a convoy of rebel mercenaries already more than half way towards Moscow in a lightning advance after seizing a southern city overnight. President Vladimir Putin vowed to crush an armed mutiny he compared to Russia’s Civil War a century ago. Fighters from Yevgeny Prigozhin’s private…
