KYIV, Ukraine — Ukrainian drone strikes damaged energy networks in Russia-occupied parts of southern Ukraine, leaving hundreds of thousands of people without power on Sunday, according to Kremlin-installed authorities there. Meanwhile, Moscow has kept up its hammering of Ukraine’s energy grid in overnight attacks that killed at least two people, according to Ukrainian officials. More than 200,000 households in the Russia-held part of Ukraine’s southern Zaporizhzhia region had no electricity on