The mayor of Kiev, Vitali Klitschko, has joined his fellow former boxing champion brother Wladimir in speaking about the Russian military operation in Ukraine, while current title holder Oleksandr Usyk has admitted he is "really emotional" and called for unity.
Ex-heavyweight king Klitschko became mayor of the city in 2014 and has regularly issued messages on social media amid political tensions between Russia and Ukraine.
Standing alongside his younger sibling, the 50-year-old pledged to "fight for freedom and democracy", praised Ukrainian military forces and pledged to protect the city.
Usyk said that some fans had accused him of "running away" by visiting London, where he beat Anthony Joshua to sensationally claim the heavyweight title in September, for a meeting earlier this week.
Ukrainian President Volodymyr Zelensky has banned men between 18 and 60 from leaving his country since the Russian military initiative began.
"I was at work but I'm back, I'm home," Usyk said in an Instagram video translated by ESPN.
"Friends, we have to unite because it's a hard time right now and I'm really emotional and worried about my country and our people."
Revered three-time champion and two-time Olympic gold medalist Vasiliy Lomachenko has reportedly fled Ukraine for Greece.
"The situation in Ukraine escalated a lot in the last couple of days," he was quoted by the outlet as saying, adding that he was trying to focus on his next fight rather than the news.
"My family is there in the middle of everything. But I am going to have my people there and my family is safe."
Usyk added a photo of himself in Ukraine and added the caption "no war".
The 35-year-old is reportedly close to confirming a rematch with Joshua, although he denied claims by WBC champion Tyson Fury this week that he is ducking him, offering to fight the Mancunian in a bare-knuckle brawl.