Ukraine invasion: Russian shelling sparks fire in eastern city of Sievierodonetsk

Russian shelling of the Azot chemical plant in the eastern Ukrainian city of Sievierodonetsk caused a strong fire on Saturday after a leak of tonnes of oil, the regional governor said, as the battle for the city raged on.

Russian forces' bid to seize Sievierodonetsk has become one of the bloodiest battles since their February 24 invasion, with neither side delivering a knock-out blow in weeks of fighting that has pulverised chunks of the city.

The governor of Luhansk province, Serhiy Gaidai, did not say if the fire at the plant, where hundreds of civilians are sheltering, had been extinguished. Reuters could not independently verify the report.

Speaking on national television, Gaidai said non-stop fighting was raging in Sievierodonetsk, a small city in Luhansk that has become the focus of Russia's advance in eastern Ukraine. He said earlier on Saturday that Russian forces controlled most of the city but Ukraine controlled the Azot chemical plant.

Ukraine has appealed for swifter deliveries of heavy weapons from the West to turn the tide of the war, saying Russian forces have at least 10 times more artillery pieces than Ukrainian forces. Yet even when outgunned, Ukraine's army has proved more resilient than expected in early phases of fighting.

President Volodymyr Zelensky struck a defiant note on Saturday.

"We are definitely going to prevail in this war that Russia has started," Zelensky told a conference in Singapore via video link. "It is on the battlefields in Ukraine that the future rules of this world are being decided."

After Russia was forced to scale back its initial more sweeping campaign goals, Moscow has turned to expanding control in the east, where pro-Russian separatists had already held a swathe of territory since 2014.

The eastern region known as the Donbas includes the provinces of Luhansk, where Sievierodonetsk lies, and Donetsk.

Russian strikes knocked out power supplies in Donetsk's two largest Ukrainian-controlled cities on Saturday, Kramatorsk and Sloviansk, regional Governor Pavlo Kyrylenko wrote on the Telegram app.

Speaking later on national television, he said the move was part of a deliberate strategy to cut off electricity in towns in Donetsk that remain in Ukrainian hands. "The enemy understands where he is hitting, and for what purpose,” he said.