"They're really insane. It's important that this doesn't go unpunished for Russia," Zelensky said.

Zelenskyy has warned of a possible Russian Oreshnik strike and urged the public to remain vigilant and use shelters.

Citing Ukrainian and Western intelligence reports, Zelensky said Russia appeared to be preparing an Oreshnik missile strike on Ukraine.

Russian forces launched a large-scale missile attack on Kyiv overnight on May 24, officials reported.