Key developments on Sept. 1: * Ukraine liberates village of Novoekonomichne in Donetsk Oblast, General Staff says * Russian front-line advances have slowed down in August, monitoring group says * Russian forces allegedly preparing major assault toward Siversk in Donetsk Oblast, Ukraine's military says * Ukraine says it destroyed 2 Russian Mi-8 helicopters, hit tugboat in occupied Crimea, shares footage * Zelensky announces faster air defense deliveries after deadly Russian strikes Ukraine