MOSCOW, MAY 30 - A military helicopter Mi-8 crashed last night in the Rivne region of western Ukraine, killing the four soldiers on board. Among the people who lost their lives is the commander of the 16th air force ground brigade, based in Brody, in the Lviv region. The causes of the tragedy are not yet clear. Ukrainian President Volodymyr Zelensky brought his condolences to the families of the victims and ordered an investigation by the armed forces. "Our army - Zelensky said - should not lose soldiers during trials and exercises".