Vitali Klitschko has revealed that he and brother Wladimir have already been forced to kill Russian soldiers since Ukraine was invaded last week.
Eight days ago, Russia president Vladimir Putin ordered mass troops to cross the border, forcing thousands of Ukrainian civilians to defend their homes and country.
Vitali, the mayor of Kyiv, has remained in the capital alongside his brother, and the elder sibling of the famous boxing brothers has claimed that they have killed as many as six Russian soldiers over the past week.
Speaking to CNN, Vitali said: "We're not interested in how strong the Russian army is, we're ready to fight, and we're ready to die for our home country and for our families because it's our home.
"It's our future and somebody wants to come to our home and steal our future from us."
Fellow boxers Vasyl Lomachenko and Oleksandr Usyk, as well as tennis player Sergiy Stakhovsky, have also taken to the streets of Ukraine in a show of solidarity. body check tags ::
