The Azot chemical facility in Sievierodonetsk, where hundreds of people are sheltering, remains under Ukrainian control, according to the region’s governor, after a Russia-backed rebel claimed 300-400 Ukrainian fighters were also besieged inside.

On the Telegram messaging app, Serhiy Gaidai, governor of the Luhansk region partially controlled by pro-Russian separatists, claimed, “The information about the siege of the Azot facility is a fabrication.”

“Our forces are holding an industrial zone of Sievierodonetsk and are destroying the Russian army in the town,” he wrote.

Sievierodonetsk, a small city in the region, has become the focus of Russia’s advance in eastern Ukraine and one of the bloodiest flashpoints in a war now into its fourth month.

Ukraine has said some 800 people were hiding in several bomb shelters underneath the Azot plant, including about 200 employees and 600 residents of Sievierodonetsk.

Rodion Miroshnik, a Russian-backed representative of the self-proclaimed Luhansk People’s Republic, said on Saturday that 300 to 400 Ukrainian fighters were blockaded on the grounds of the plant along with civilians and had tried to negotiate their passage to the city of Lysychansk.

“Such demands are unacceptable and will not be discussed,” Miroshnik said, adding that negotiations with fighters about civilians at the plant were under way.