According to Ukrainian police, Brent Renaud was traveling in a car with colleagues when Russian forces opened fire.
Two more journalists are said to have been injured in the attack, the Kiev police chief states.
One of the gunshot wounded journalists confirms the attack in a video that is spread on social media.
Initially, information was spread that Renaud was in Ukraine on behalf of the New York Times, this when he wore a press ID issued by the newspaper.
According to the newspaper, he has worked for them several times over the years, most recently in 2015. New York Times Deputy Editor-in-Chief Cliff Levy wrote on Twitter that he is "deeply saddened" and describes the journalist as a "talented photographer and filmmaker".
Award-winning filmmaker
Renaud, who turned 50, has previously worked for a number of American news and media organizations, including HBO, NBC and The New York Times.
Among other things, he has reported from the war in Iraq and Afghanistan.
In 2015, he and his brother Craig Renaud won a Peabody Award for the documentary "Last Chance High".
Anton Gerashchenko, adviser to Ukraine's interior minister, said in a statement that Renaud "paid with his life for trying to expose the attacker's insidiousness, cruelty and ruthlessness."