At least four people died in an apartment building in downtown Kyiv on Monday when Russia attacked Ukrainian cities with drones during morning rush hour, also targeting infrastructure across the country in a second large wave of air strikes in a week.
An adviser to Ukrainian President Mykhailo Podolyak said Iran was responsible for "murders of Ukrainians" after the Russian attack, with what Kyiv said were drones made in Iran.
Ukraine has reported a spate of Russian attacks using Iranian-made Shahed-136 drones in recent weeks. Iran denies supplying the drones to Russia, while the Kremlin has not commented.
"Iran is responsible for the murders of Ukrainians. Country that oppresses its own people is now giving ru-monsters weapons for mass murders in the heart of Europe. That is what unfinished business and concessions to totalitarianism mean. The case when sanctions are not enough," Podolyak wrote on Twitter.
Ukrainian soldiers fired into the air trying to shoot down the drones after blasts rocked central Kyiv. An anti-aircraft rocket could be seen streaking into the morning sky, followed by an explosion and orange flames, as residents raced for shelter.
A pregnant woman was among three people killed in the attack on the residential building, Kyiv mayor Vitali Klitschko said. Ukraine's Interior Minister Denys Monastyrskyi said there had been deaths in other cities but did not give a full toll.
Black smoke poured out of the windows of the Kyiv apartment building and emergency service workers toiled to douse flames.
"I have never been so afraid... It is murder, it is simply murder, there are no other words for it," said Vitalii Dushevskiy, 29, a food delivery courier who rents an apartment in the blasted building.
His flat mate, who gave his name only as Nazar, said they had tried to leave their flat only to find the staircase "all gone".
Nearby, Elena Mazur, 52, was searching for her mother, who had managed to call her to say she was buried under rubble.
"She is not picking up the phone," Mazur said, hoping she had been rescued and taken to hospital.
Ukraine said the attacks were carried out by Iran-made 'suicide drones', which fly to their target and detonate. Russia's defense ministry said it had carried out a "massive" attack on military targets and energy infrastructure across Ukraine using high-precision weapons.
"All night and all morning the enemy terrorizes the civilian population. Kamikaze drones and missiles are attacking all of Ukraine," President Volodymyr Zelenskiy said on the Telegram messaging app.
"The enemy can attack our cities, but it won't be able to break us. The occupiers will get only fair punishment and condemnation of future generations. And we will get victory."
Reuters saw pieces of a drone used in the attack that bore the words: "For Belgorod" - an apparent reference to Ukrainian shelling of a Russian region bordering Ukraine.
The strikes came exactly one week after Russia unleashed its heaviest aerial bombardment of Kyiv and other Ukrainian cities since the start of the war - also during morning rush hour.
"This is already a tradition: to wake Ukrainians with missiles on Mondays," said Alla Voloshko, a 47-year-old lawyer who took shelter in the basement of her apartment block.
Ukraine's military said it had destroyed 37 Russian drones since Sunday evening, or around 85% of those used in attacks.
A drone attack hit the Everi marine terminal in the southern city of Mykolaiv late on Sunday, officials said, damaging sunflower storage tanks and setting aflame leaking oil.
"This is an entirely civilian facility. There is no military," said Andriy, 47, a senior manager who declined to give his last name. He said the attacks were part of a Russian effort to "destroy the economy and to destroy food security".
The new United Nations human rights chief, Volker Turk of Austria, said drone attacks on civilians had to stop.
Russia denies targeting civilians in its "special military operation" in Ukraine, now in its eighth month.
Iran repeated on Monday its denial that it is supplying the drones to Russia.
Some European Union foreign ministers, in Luxembourg for talks, called for new sanctions against Iran if Tehran's involvement in Russia's war on Ukraine is proven.