STORY: Captain Sviatoslav Palamar, 39, a deputy commander, spoke in an interview with Reuters from the steel works that is the last redoubt for the port city's defenders.
Russian forces have reduced large parts of Mariupol to ruins around the vast complex and its underground catacombs, where Palamar and a Ukrainian contingent are making a last stand.
Russian President Vladimir Putin, who claimed control of the city last week, said the plant should be sealed off so that "not a fly" could escape.
The capture of Mariupol, on the Sea of Azov in the south of the industrial Donbas region, is crucial to Russian efforts to secure a land bridge to the Crimean peninsula it seized from Ukraine in 2014.
Palamar, speaking to Reuters by Zoom, said he could not turn the camera on the call to show his quarters in case it gave away any intelligence to the Russians.
The Azov fighters in the steel works included Russians, Bulgarians, a Crimean Tatar, a Greek, Jews, Catholics and others, he said.
He said his main message to the world was to wake up to the threat from Russia and to stop being soft on Moscow.