KYIV/KONSTYANTYNIVKA, Ukraine (Reuters) – Fighting intensified for Lysychansk, Ukraine’s last major stronghold in the strategic eastern province of Luhansk, as an adviser to President Volodymyr Zelenskiy admitted the city could fall. Explosions also rocked the Russian city of Belgorod, near the border with Ukraine, the regional governor said early Sunday. The explosions set fire to a residential building and three injured people were taken to a hospital, Vyacheslav Gladkov said on the Telegram messaging app. Russia is seeking to expel Ukrainian forces from Luhansk and Donetsk provinces in the Donbass, where Moscow-backed separatists have been fighting Kyiv since Russia’s first military intervention in Ukraine in 2014. Ukrainian troops on the eastern frontline describe heavy artillery barrages in residential areas, while Kyiv says Moscow has stepped up missile attacks on towns far from the main eastern battlegrounds, accusing Russia of deliberately hitting civilian sites. Thousands of civilians have been killed and cities leveled since Russia invaded Ukraine on February 24 in what its Western allies in Ukraine say is an unprovoked war of aggression. Russia denies targeting civilians in what President Vladimir Putin calls a “special military operation” to demilitarize and “de-Nazitize” its neighbor. Russian forces captured Lysychansk’s sister city of Sievierodonetsk, on the opposite side of the Siverskiy Donets River, last month after some of the fiercest fighting of the war. Rodion Mirosnik, ambassador to Russia of the self-proclaimed Luhansk People’s Republic, told Russian television, “Lysychansk has been brought under control,” but added, “Unfortunately, it has not been liberated yet.” Russian media showed video of Luhansk militiamen marching through the streets of Lysychansk waving flags and cheering, but Ukrainian National Guard spokesman Ruslan Muzychuk told Ukrainian television that the city remained in Ukrainian hands. The story continues “Now there is fierce fighting near Lysychansk, however, fortunately, the city is not surrounded and is under the control of the Ukrainian army,” Muzychuk said. Reuters could not independently verify reports on the battlefield. Zelenskiy adviser Oleksiy Arestovych said Russian forces had finally crossed the Siverskiy Donets River and were approaching the city from the north. “This is indeed a threat. We’ll see. I’m not ruling out any of the different outcomes here. Things will become much clearer in a day or two,” he said. Arestovych said, however, that taking Lysychansk would complicate matters strategically for the Russians, as they would have to focus on six major cities in the industrialized eastern Donbas region, spreading their forces more thinly. He added: “The more Western weapons come to the front, the more the picture changes in favor of Ukraine.” Ukraine has repeatedly appealed for more weapons from the West, saying its forces are heavily armed. ‘VERY DIFFICULT ROAD’ Away from the fighting in the east, Russia said it hit army command posts in Mykolaiv near the vital Black Sea port of Odessa, where the mayor on Saturday had reported heavy explosions. Ukrainian authorities said another rocket hit an apartment building near Odessa on Friday, killing at least 21 people. A shopping center was hit on Monday in the central city of Kremenchuk, killing at least 19. Zelensky denounced the strikes on Friday as “conscious, deliberately targeted Russian terrorism and not some kind of mistake or accidental missile strike.” In his late-night televised address on Saturday, Zelensky said it would be a “very difficult road” to victory, but Ukrainians must maintain their resolve and inflict casualties on “the aggressor … so that every Russian remembers that Ukraine it cannot be broken.” Troops on a break from fighting in Konstyantynivka, a town about 115 km west of Lysychansk, said they had managed to keep the supply route to the embattled town open for now despite Russian shelling. “We still use the road because we have to, but it’s within artillery range of the Russians,” said one soldier as comrades relaxed nearby, eating sandwiches or eating ice cream. “The Russian tactic right now is to bomb any building we could be in. When they destroy it, they move on to the next one,” he said. Reuters reporters saw an unexploded rocket fall to the ground in a residential neighborhood on the outskirts of the Donbas city of Kramatorsk on Saturday night. The missile landed in a wooded area between residential towers. Outgoing artillery fire and several large explosions were heard in central Kramatorsk earlier in the evening. Despite being battered in the east, Ukrainian forces have made some progress elsewhere, including forcing Russia to withdraw from Snake Island, a Black Sea outcropping southeast of Odessa that Moscow seized at the start of the war. Russia had used Snake Island to impose a blockade on Ukraine, one of the world’s largest grain exporters and a major producer of vegetable oil seeds. The disruptions helped drive up grain and food prices worldwide. Russia, also a major grain producer, blames the crisis on Western sanctions that hit its exports. (Reporting by Reuters offices; Writing by David Brunnstrom and Lincoln Feast; Editing by William Mallard)