The mayor of Mariupol said on television Wednesday that he has lost contact with Ukrainian forces in the besieged city's steel factory.
"Today, there are heavy battles on the territory of our fortress, on the territory of Azovstal. Our brave guys are defending this fortress, but it is very difficult, because heavy artillery and tanks are firing all over the fortress," Mariuopol Mayor Vadym Boichenko said on Ukrainian TV.
He added: "Aviation is working, ships have approached and are also firing on the fortress," adding that children were among the civilians still trapped inside.
For weeks, civilians and some Ukrainian troops have been holed up at the Azovstal steel plant in Mariupol, which has been surrounded by Russian military forces.
Dozens of civilians were evacuated from the strategic port city Tuesday as Russian forces finally stormed the facility.
"Unfortunately, there is no connection with the guys today, there is no possibility to reach out to them to understand what is happening, whether they are safe or not," Boichenko said.
"We pray for our heroic defenders and thank them for the heroic actions they are doing today for our entire country. They restrained the enemy and gave us more time to prepare."
Denys Shlega, a Ukrainian National Guard commander, said "the enemy is trying to storm the Azovstal plant with significant forces using armored vehicles," the New York Post reported.
Russia began Wednesday by firing incendiary rockets into Kharkiv, igniting a large fire in a civilian neighborhood Ukraine's second-largest city, while also ramping up missile attacks across the battle-scarred country.
More than 20 people were killed in the eastern Donetsk region, Ukrainian officials said, and Russian cruise missiles targeted infrastructure in Lviv in western Ukraine.
Ukrainian officials say that Russian forces are preparing for a May 9 Victory Day parade in Mariupol. Victory Day is held every May 9 in Russia to celebrate the Allied victory in World War II over Nazi Germany.
Mariupol has been one of Moscow's top targets since the fighting began Feb. 24.
