Shelling by Russian forces has caused a massive fire at a chemical plant in the besieged eastern Ukrainian city of Syevyerodonetsk, the local governor said, as Ukrainian leaders continued to plea for additional weapons to fight off the onslaught by invading forces throughout the region.

Speaking on June 11 on national television, Luhansk regional governor Serhiy Hayday did not indicate if the fire at the Azot chemical plant had yet been extinguished, but he said fighting continued to rage in the city, where Ukrainian forces were attempting to push back Russian troops conducting a major offensive against the city.

Hayday said Russian forces controlled some 90 percent of the strategic city but that Ukrainian troops were holding out at the chemical plant.

Moscow-backed separatist fighters earlier said they had surrounded the site and that the defenders were trapped.

"A small group of Ukrainian formations on the territory of the Azot chemical plant can no longer leave the factory. All escape routes are cut off for them," Rodion Miroshnik, a separatist official in the Luhansk region, wrote on Telegram. He acknowledged that civilians could also be holding out in the plant.

The claims could not be independently confirmed.

The siege was reminiscent of what occurred in the port city of Mariupol, where residents and fighters took cover in and below the Azovstal steel plant before being surrounded and eventually surrendering to Russian forces after brutal fighting.

Ukrainian President Volodymyr Zelenskiy, meanwhile, renewed his call for Western countries to speed deliveries of weapons as Russian forces pounded much of the east of the country.

Ukrainian troops "are doing everything to stop the offensive, as much as they possibly can, as long as there are enough heavy weapons, modern artillery -- all that we have asked for and continue to ask for from our partners," Zelenskiy said in his nightly video address on June 10.

Zelenskiy said that "very difficult battles" were ongoing, including in the eastern Donbas region, where Moscow has concentrated its firepower.

Zelenskiy said Russia wants to destroy every city in the Donbas.

"Every city, that’s not an exaggeration. Like Volnovakha, like Mariupol. All of these ruins of once-happy cities, the black traces of fires, the craters from explosions -- this is all that Russia can give to its neighbors, to Europe, to the world."

The fiercest fighting remains around Syevyerodonetsk, a small industrial city that has become the focus of Russia's advance in eastern Ukraine.

Britain's Ministry of Defense said in its daily intelligence bulletin on June 11 that the Russians had not made advances into the south of the city.

"Intense street to street fighting is ongoing and both sides are likely suffering high numbers of casualties," the ministry said in an intelligence update posted on Twitter.

The update said Russian bombers had likely been launching 1960s-era heavy, anti-ship missiles meant to destroy aircraft carriers with nuclear warheads against land targets in Ukraine. It added that Russia is likely using such weapons because it is running short of more precise modern missiles.

Also on June 11, the Ukrainian Army said that Russian forces were regrouping to launch an offensive on the city of Slovyansk in the eastern Donetsk region.

In its regular operational update, the Ukraine's General Staff said Moscow managed to get a foothold overnight in the village of Bohorodychne, 24 kilometers northwest of Slovyansk, and was preparing to attack the city.

The war in the east is now primarily an artillery battle in which Kyiv is severely outgunned, Ukrainian officials say.

"This is an artillery war now," Vadym Skibitsky, Ukraine's deputy head of military intelligence, told The Guardian.

"Everything now depends on what [the West] gives us. Ukraine has one artillery piece to 10 to 15 Russian artillery pieces."

Germany plans to revise its rules on arms exports to make it easier to arm democracies like Ukraine, Der Spiegel reported on June 10. Berlin has been among the largest suppliers of weapons since Russia invaded but criticized for being slow to supply heavy weaponry to Kyiv.

Another German publication, Bild am Sonntag, reported on June 11 that German Chancellor Olaf Scholz will travel to Kyiv along with France's Emmanuel Macron and Italian Prime Minister Mario Draghi sometime before the Group of Seven summit at the end of June.

German officials said they could not confirm the report.

Ukraine also asked for humanitarian support to combat an outbreak of dysentery and cholera in the port city of Mariupol, which has been reduced to ruins.

Mayor Vadym Boychenko told national television that sanitation systems were broken and corpses were rotting in the streets.

"Unfortunately...these infection outbreaks will claim thousands more Mariupolites," Boychenko said.

The Ukrainian Prosecutor-General's Office said on June 11 that it has learned about the deaths of 24 more children in Mariupol as the result of shelling by Russian forces.

In total, the office said that at least 287 children have died since the start of the Russian invasion of Ukraine on February 24. More than 492 have been wounded, according to the tally.

Meanwhile, on June 11, U.S. Defense Secretary Lloyd Austin reinforced Washington's commitment to the region in light of the war.

"Russia’s invasion of Ukraine is what happens when oppressors trample the rules that protect us all," Austin told an Asian security forum in Singapore. "It's a preview of a possible world of chaos and turmoil that none of us would want to live in."

With reporting by Reuters, AFP, and AP