Ukraine launched a stunning wave of drone attacks on Russia and annexed Crimea overnight, killing at least two people and setting an oil refinery ablaze, Russian officials said Friday.The attack was Kyiv's largest aerial offensive in recent weeks and comes as Russian forces advance along the front line in northeastern Ukraine, taking advantage of Ukraine’s manpower shortages and delays in shipments of U.S.

military aid.Russia’s Defense Ministry said it had intercepted or destroyed more than 100 Ukrainian air and seaborne drones in the south of the country, as well as in annexed Crimea and the Black Sea."Fifty-one unmanned aerial vehicles were destroyed and intercepted over Crimea, 44 over the Krasnodar region, six over the Belgorod region, and one over Kursk region," the Defense Ministry said, adding that the Russian navy destroyed six seaborne drones.One drone struck the care of a family that was driving near the border in western Russia's Belgorod region, killing a mother and her four-year-old son, the region's governor Vyacheslav Gladkov said."The child was in critical condition.

Doctors did everything they could to save him," Gladkov said.

"With great regret, the four-year-old died at the hospital."Gladkov said the father of the child was injured and "in a state of shock,” while the driver of the car was treated for shrapnel wounds to his hands.Another drone attack caused a fire at a gas station in the village of Bessonovka, but the flames were quickly put out, according to the governor.In the coastal town of Tuapse in the southern Krasnodar region, two Ukrainian drones hit an oil refinery, sparking a large fire but without causing any casualties, authorities said.The port city of Sevastopol in annexed Crimea experienced a "partial blackout" after debris from downed drones fell on an electrical substation, the city's Russian-installed governor Mikhail Razvozhayev said."While restoration work continues, the city will not be able to receive enough energy.

There will be isolated blackouts," he warned, adding that schools would cancel classes.The overnight drone attacks come as Russian forces push further into Ukraine's northeastern Kharkiv region after pouring across the border in a fresh offensive last week.Ukraine has evacuated almost 9,000 civilians from the border area, as Russia advances towards Vovchansk and nearby villages.