The Klitschko brothers walked to the front line in Kiev ahead of a Russian siege and said they were “ready to die for Ukraine”.
Vitali and his former world heavyweight boxing champion brother Wladimir visited a military checkpoint on the outskirts of the capital on Sunday.
Footage from the front line shows Vitali, who is Kyiv’s mayor, and his brother being escorted around the checkpoint in body armor by Ukrainian defenders.
The visit comes as Vitaly has claimed he is ready to die defending the capital.
The 50-year-old took up arms alongside his younger brother and will only leave his capital victorious or dead.
“I’m very proud to see how patriotic people are,” he told CNN. “We are not interested in the strength of the Russian army, we are ready to fight.
“And we are ready to die for our country of origin and for our families, because it is our home.
“This is our future and someone wants to come to our house and steal our future.”
When asked how long he thought his makeshift army could hold off Vladimir Putin’s marauding thugs, he admitted his own mortality was part of the equation.
“I’m not ready to give you a straight answer,” he said. “So long, so long — if we are still alive”.
The two former heavyweight champions told Sky News they have already killed six people in the capital where Ukrainian troops are trying to eliminate separate Russian groups.