First responders who arrived at the scene of a Russian missile attack on homes in the southern Ukrainian city of Odesa on Friday were themselves struck by a second missile, officials said.
A paramedic and an emergency service worker were among the 16 people killed.
Officials said 53 other people were wounded in the attack on houses in the port city.
The attack occurred as Russians voted in a presidential election that is all but certain to extend Vladimir Putin’s rule by another six years after he crushed dissent, and as the war in Ukraine stretches into its third year.
At least 10 houses in Odesa and some emergency service equipment were damaged in the attack, which started a blaze, according to Ukraine’s Emergency Service and regional governor Oleh Kiper.
The tactic of firing a second missile at the same location, aiming to hit rescuers, is known in military terms as a double tap. Such strikes often hit civilians.
Mr Kiper announced that a day of mourning in Odesa will be held on Saturday – the second such observance in less than two weeks.
On March 2, a Russian drone struck a multi-storey building, killing 12 people, including five children.
Since last summer, Russia has intensified its attacks on Odesa, a southern port city with a population of around one million residents.
The attacks have primarily targeted port infrastructure, aiming to disrupt the export of goods after Ukraine managed to restore maritime navigation with a series of successful operations in the Black Sea.
Moscow officials have also claimed they are aiming at facilities where Ukrainian sea drones are stored for attacks on Russia’s Black Sea fleet.
The Odesa region’s ports were key to last year’s international agreement that let Ukraine and Russia ship their grain to the rest of the world.
The city’s residents largely speak Russian and its past is intertwined with some of Russia’s most revered figures, including Catherine the Great, author Leo Tolstoy and poet Anna Akhmatova.
Its Orthodox cathedral belongs to Moscow’s patriarchate and — at least until the Kremlin illegally annexed the nearby Crimean Peninsula in 2014 — its beaches were beloved by Russian tourists.
Meanwhile, in the Russian border region of Belgorod, regional governor Vyacheslav Gladkov said a member of the regional territorial defence forces was killed and two people were injured in Ukrainian shelling on Friday.
Overnight in Ukraine, two people were also killed and three wounded in the central region of Vinnytsia after Russia struck a building with a drone, according to regional governor Serhii Borzov.
The Ukrainian air force said it shot down all 27 Shahed drones that Russia launched over the Kharkiv, Vinnytsia, Kirovohrad, Mykolaiv, Khmelnytskyi and Kyiv regions.