Ukrainian President Volodymyr Zelensky has called Wednesday's helicopter crash in Brovary "a terrible tragedy."
Zelensky confirmed that interior minister Denis Monastyrsky, first deputy minister Yevheniy Yenin and state secretary Yuriy Lubkovychis all died in the crash in a statement published Wednesday.
He said he has ordered the Ukrainian security services to "find out all the circumstances" of the incident.
The Interior Ministry officials were "true patriots of Ukraine," he said.
"May they rest in peace! May all those whose lives were taken this black morning rest in peace," he added.
Ukraine's first lady Olena Zelenska called it a "horrible day" for the country.
“In helicopter crash we lost the Interior Minister and his colleagues – but the biggest tragedy is a death of children. They have faith that we, as adults, are able to protect them. My thoughts are with the victims’ families. Wish the injured speedy recovery,” she tweeted.
CNN's Alex Hardie contributed reporting to this post.