KYIV -- A suspected Ukrainian drone attack has caused a brief fire at an oil refinery in southern Russia's Volgograd region, according to a local official.
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"The fire was extinguished. There were no casualties,” regional Governor Andrei Bocharov said on Telegram on May 12.
Telegram channels close to Russian security services posted images showing flames rising from what appeared to be an industrial building at the site of the incident.
Neither the Russian energy giant LUKoil, which owns the refinery, nor Kyiv has commented on the incident.
The attack came just hours after Ukrainian President Volodymyr Zelenskiy raised alarms about frontline conditions in the war against Russia.
Zelenskiy said during his nightly video address on May 11 that the situation in the eastern Donetsk region was "especially tense." In the northeastern Kharkiv region, meanwhile, thousands of local residents have reportedly been forced to flee in the face of relentless Russian air assaults.
"Today, the focus is primarily on the front line – on the situation in our regions where the risks of the Russian offensive actions are the highest," Zelenskiy said.
Zelenskiy stated that "defensive operations" were under way in the Kharkiv region, naming several villages near the border with Russia, and saying his forces were "bravely defending their positions."
Russian shelling in the region led the Ukrainian military to declare an air alert over most of the country, and Kharkiv authorities said on May 12 that more than 4,000 people had been evacuated.
The Ukrainian General Staff early on May 11 cited more than 100 areas of fighting in the previous 24 hours, in addition to overnight missile and drone attacks, hinting at the intensity of the Russian campaign 27 months into the full-scale invasion.
On May 10, Russian troops attempted to open a new front by breaking through Ukrainian lines in the northeastern Kharkiv region, a move Kyiv said its forces repelled, though fighting was reported to be continuing.
Ukraine's military was reportedly speeding reinforcements to the area, as local residents expressed shock over the scale of the attacks.
Residents of the Ukrainian town of Vovchansk near the Russian border said on May 11 that overnight strikes caused shortages of food, water, and fuel. Vovchansk, with a prewar population of about 17,500 people, is northeast of Kharkiv and about 6 kilometers from the border.
"It has already become really scary. All life is here: my grandchildren, children,” Antonina Kornuta told RFE/RL. “I don't want to evacuate."
Valeriy Dubskiy told RFE/RL that “water sources are far away and people must wait in long lines. You cannot get water after such bombardment. We are running away from the shelling, from the bombardment, from death -- from the Russian death."
Another female resident said that "planes dropped a lot of bombs on the town during the night. It looked as if the sky had exploded. It was very scary, very noisy."
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Hundreds In Kharkiv Flee Their Homes To Escape Russian Shelling
Russia's Defense Ministry on May 11 claimed to have captured six border communities around Kharkiv -- Pletenivka, Ohirtseve, Borysivka, Pylna, and Strilecha -- and the village of Keramik in the Donetsk region.
But the Ukrainian side did not confirm such losses and RFE/RL could not independently verify the Russian assertion.
Russia has expanded its use of advanced rockets and missiles in addition to barrages from unmanned attack drones and recently has specifically targeted power infrastructure even far from the front lines.
Moscow denies targeting civilians, but Russian air strikes have frequently hit hospitals, schools, and residential areas with devastating effect.