Brent Renaud, 50, was a journalist and filmmaker who had previously worked for the New York Times.
Kyiv’s police chief Andriy Nebytov said he had been targeted by Russian soldiers. Two other journalists were injured and taken to hospital.
It is the first reported death of a foreign journalist covering the war in Ukraine.
One of the injured journalists, Juan Arredondo, told an Italian reporter that he was with Brent Renaud when they came under fire.
“We were across one of the first bridges in Irpin, going to film other refugees leaving, and we got into a car”, he said in a video published on Twitter.
“Somebody offered to take us to the other bridge and we crossed a checkpoint, and they start shooting at us. So the driver turned around, and they kept shooting; there’s two of us. My friend is Brent Renaud, and he’s been shot and left behind… I saw him being shot in the neck.”
Photographs are circulating online showing a press ID for Renaud that was issued by the New York Times.
In a statement, the newspaper said it was “deeply saddened” to hear of Renaud’s death but that he had not been working for the newspaper in Ukraine.
Renaud last worked for the publication in 2015, the Times said, and the press ID he was wearing in Ukraine had been issued years ago.
NBC News said their “thoughts and prayers” were with Renaud’s family and praised the “important contributions” he made to NBC News reports, adding that he was not working for them in Ukraine.
‘Tell the world what they did’
Renaud had worked for a number of US news organisations and had reported from Afghanistan, Iraq and Haiti. He won a Peabody Award for his work on a 2014 series on Chicago schools, Last Chance High.
He often worked alongside his brother, Craig, also a filmmaker, and was based in New York and Little Rock, Arkansas. It is not known whether Craig had also travelled to Ukraine.
A Ukrainian police officer told PBS news journalist Jane Ferguson to “tell America, tell the world, what they did to a journalist”.
US National Security Adviser Jake Sullivan told CBS News that the country could impose “appropriate consequences” against Russia for Renaud’s death.
“This is part and parcel of what has been a brazen aggression on the part of the Russians, where they have targeted civilians, they have targeted hospitals, they have targeted places of worship, and they have targeted journalists,” he said.
Renaud’s death comes less than two weeks after Ukrainian journalist Yevhenii Skaum, a camera operator for the Ukrainian television channel LIVE, was killed when a TV transmission tower in Kviv was hit by shelling.
A few days later, a British journalist covering the war in Ukraine was shot and wounded after coming under fire in Kyiv.
Sky News chief correspondent Stuart Ramsay and his four colleagues were driving back to the Ukrainian capital when they were ambushed.
