Ukrainian President Volodymyr Zelensky addresses the nation in Kyiv early on February 25, 2022. AFP
In a video address released early Friday, Zelensky called them "heroes'' in which he also says hundreds more have been wounded.
Zelenskyy said that despite Russia's claim it is attacking only military targets, civilian sites also have been struck.
In his words: "They're killing people and turning peaceful cities into military targets. It's foul and will never be forgiven.''
The president says all border guards on Zmiinyi island in the Odesa region were killed Thursday.
Ukraine's border guard service earlier in the day reported that the island was taken by the Russians.