Deadly helicopter crash 'a tragedy', Kyiv mayor

STORY: Speaking after an event with Ukrainian first lady Olena Zelenska and other officials, Klitschko remembered Interior Minister Denys Monastyrskyi as a "very patriotic guy, doing a lot of things for Ukraine."

Ukrainian officials said nine people on board the aircraft and six on the ground, including three children, were killed when the French-made Super Puma helicopter crashed in a residential area in the suburb of Brovary on the capital's eastern outskirts.

It was not immediately clear what caused the helicopter to crash. There was no immediate comment from Russia, which invaded Ukraine last February, and Ukrainian officials made no reference to any Russian attack in the area at the time.

"We need to investigate, exactly investigate what really happened, but right now I don't have any information," Klitschko said.