Ukrainian officials say Russian forces have launched an all-out assault on the Azovstal steelworks, the last Ukrainian holdout in the city of Mariupol.
Ukrainian forces inside the plant have been fighting "difficult bloody battles" for a second day, the commander of the Azov regiment said.
Russian forces are reported to have entered "the territory of the plant" after days of sustained attacks.
About 200 civilians are believed to be sheltering inside, including children.
The BBC has not been able to verify the reports of the Russian attack on the steel plant.
In a brief video message posted on Telegram, Azov commander Denis Prokopenko said: "I am proud of my soldiers who are making superhuman efforts to contain the pressure of the enemy... the situation is extremely difficult."
President Volodymyr Zelensky has made a further appeal to the UN to help save the lives of those who remain there.
