Kyiv Mayor Vitali Klitschko tells CNN's Erin Burnett he worries about the possibility of Russian President Vladimir Putin using a tactical nuclear weapon on Kyiv.
"Safety is the main priority right now ...Yes of course we worry, and we hope our warriors defend us, but the risk is still there and without our partners, without United States and European countries we can't survive," Klitschko said.
He also said there is "no doubt" the capital of Ukraine is still Russia's "main target."
The mayor warns residents coming back to Kyiv to be cautious saying, "... as mayor of Kyiv I tell to anyone, sorry, it's your personal risk, but we can't give you guarantee ... So long as there's war in Ukraine we can't give the guarantee for any Ukrainian."
He said Russian attacks could happen "any second."
Klitschko added that war "changed life for everyone" and he says he is keeping his fingers crossed to "stop this senseless war as soon as possible."