French President Emmanuel Macron has confirmed two French aid workers were killed in a Russian strike in Ukraine, condemning the attack as "cowardly".
"My solidarity goes out to all the volunteers who are committed to helping people," he said in a post on X.
Ukrainian officials earlier said two foreign volunteers had been killed in the southern Beryslav town on Thursday.
Russia has not publicly commented. A number of foreign volunteers have been killed in Ukraine since the war began.
Russian President Vladimir Putin launched a full-scale invasion of its south-western neighbour in February 2022.
Referring to the incident, Ukrainian officials said another four people - including three foreign volunteers - were injured in a "massive" drone attack of the front-line town on the Dnipro River in the Kherson region.
French Foreign Minister Stéphane Séjourné later said that the three injured were also French nationals.
Russia would "answer for its crimes" and "barbarity", Mr Séjourné added.
The French volunteers have not been publicly named, and the organisation they worked for has not been revealed.
Senior Kherson official Yuriy Sobolevsky said only that the victims had been employed by a "powerful" international organisation working in more than 30 countries, according to Ukraine's Suspilne broadcaster.
In a post on X, Ukrainian President Volodymyr Zelensky wrote that "Russian terror knows no boundaries or nationalities.
"The brave French aid workers assisted people and we will always be grateful for their humanity," he added.
Beryslav, Kherson and other Ukrainian towns on the right (west) bank of the Dnipro River have been regularly attacked by Russian troops from the territory they have seized on the left bank of the region.
Two people were killed and another six injured in Russian shelling of the region over the last 24 hours, local officials said on Friday.
In September 2023, Emma Igual, the Spanish director of Road to Relief, and Anthony Ihnat, a Canadian colleague, were killed in a Russian strike in Ukraine's eastern Donetsk region.
In January 2023, British nationals Chris Parry and Andrew Bagshaw, who had been earlier reported missing in the same region, were confirmed killed. Their families said they had died while "attempting a humanitarian evacuation".