Two aid workers, one Canadian and one Spanish, were killed in eastern Ukraine, hours after the Kyiv region fended another wave of drone attacks overnight.
Ukraine's defence ministry said Moscow's troops had killed Emma Igual, a Spanish citizen who studied at the University of California at Berkeley, and Anthony Ihnat, a Canadian citizen, both working for the NGO Road to Relief.
Two other volunteers with the group -- German citizen Ruben Mavik and Swedish citizen Johan Mathias -- were injured in the incident in the eastern Donetsk region, said Kyiv.
Road to Relief said in a post on its Instagram account that the vehicle the four aid workers were travelling in "came under Russian attack" in Chasiv Yar in eastern Ukraine on Saturday morning.
In "a direct hit, the vehicle flipped over and (caught) fire," it said.
Igual, 32, was the director of Road to Relief, which she co-founded with Frenchman Henri Camenen in March 2022, just days after Russia invaded Ukraine.
Ukrainian President Volodymyr Zelensky paid tribute to the victims in his evening address Sunday.
"This Russian shelling once again confirms how close the war against Ukraine is for everyone in the world who truly values human life and who considers it a common moral duty of humanity to stop terror and defeat evil," he said.
- Drone attack -
Ukraine said on Sunday it had shot down most of the three dozen drones Russia launched overnight at the Kyiv region.
The latest attack came as Ukraine's forces were calling more Western support for their counter-offensive to gain back land in the east and south.
"We recorded the launch of 33 Shahed (drones) in the direction of Kyiv... 26 were destroyed," the Ukrainian Air Force said.
An AFP journalist in the Ukrainian capital heard multiple explosions -- presumably from air defence -- starting around 1:30 am (2230 GMT).
"Drones entered the capital in groups and from different directions," Sergiy Popko, head of the Kyiv City Military Administration, wrote on Telegram.
Four people were wounded, including one who was hospitalised with injuries to the head and limbs, Kyiv official Ruslan Kravchenko said.
More than a hundred homes were damaged by falling debris, Kravchenko added.
Ukrainian emergency services published photos of rescuers putting out fires which caught fire in several districts.
Kyiv endured drone and missile attacks almost every night this winter and spring, as Russia pounded cities across Ukraine in a bid to wipe out Ukraine's energy infrastructure and destroy morale.
The strikes tailed off until last month, when the capital faced the "most powerful strike" since spring. More than 20 drones and missiles were destroyed.
- Kyiv pushes for more -
Fierce combat is underway in the east and south of Ukraine, where Kyiv's forces are seeking to push Russian troops out of the territories they have seized.
Ukrainian officials at a conference on Friday and Saturday urged the West not to lose any time and provide Kyiv with powerful weapons to back up its forces.
A series of recent speeches by senior administration officials drew a picture of a country at war, held back by allies who had failed to grasp the scale and urgency of the crisis.
Newly appointed Defence Minister Rustem Umerov called for more military equipment.
"We are grateful for all the support provided... We need more heavy weapons," Umerov said.
"We need them today. We need them now."
Zelensky said the provision of Western weapons was slowing down, hampering the counter-offensive against Russian positions.
And Deputy Defence Minister Ganna Malyar said: "The enemy is strong. They have more people and weaponry."
On Sunday Ukrainian forces announced they had made a modest advance -- of more than a kilometre (mile) -- in an area of the southern front line.
Ukraine has been undertaking a laborious counter-assault since June, a far cry from the lightning successes it achieved in autumn 2022.
This time, Ukrainian forces are contending with well-entrenched Russian defences built over several months of occupation.
Russia is holding local and regional elections this week, both at home and in the Ukrainian regions it claims, in a bid to legitimise its annexation of the latter.
The ballots organised by Moscow-installed officials in the Ukrainian regions have been widely denounced as a sham.
Kyiv has urged its allied condemn the "fake" elections.