Ukrainian President Volodymyr Zelensky vowed on Friday to launch more retaliatory strikes on Russia, a day after a Russian strike on Kyiv killed 24 people, including three children, according to officials.
Russia has shown little sign of halting its more than four-year invasion of Ukraine, launching hundreds of drones and multiple missiles at its neighbor every day.
Kyiv has responded with its own attacks and a drone strike on the Russian city of Ryazan earlier Friday killed four people including a child, according to officials there.
US-led talks on ending Europe's deadliest conflict since World War II have stalled in recent months, while Moscow has ruled out a ceasefire or comprehensive negotiations with Kyiv unless it caves to its maximalist demands.
"Ukraine will not allow any of the aggressor's strikes that take the lives of our people to go unpunished," Zelensky said in a post on X.
"We are entirely justified in our responses against Russia's oil industry, military production, and those directly responsible for committing war crimes against Ukraine and Ukrainians," he added.
Earlier Friday, Zelensky visited the site of a building in Kyiv ripped apart by a Russian missile.
"Here, Russia took the lives of 24 people, including three children," Zelensky said, after walking through a courtyard littered with rubble.
The three children killed were all girls -- aged 12, 15 and 17.
The father of the youngest -- named as Liubava Yakovleva -- had already died fighting Russia's invasion, Ukrainian Prime Minister Yulia Svyrydenko said.
"Rescue operations lasted more than 28 hours, 30 people were thankfully saved due to the tireless efforts of our emergency workers," she said on social media.
Two dozen people were still in hospital, Kyiv Mayor Vitali Klitschko said.
- POW swap -
The scenes in Kyiv contrasted with elation in northern Ukraine, where 205 Ukrainian soldiers were freed in the latest POW exchange with Moscow.
AFP reporters saw the released fighters -- with shaven-heads and draped in Ukrainian flags -- cheering, crying, embracing one another and waiting to be reunited with their families.
Kyiv freed the same number of Russian soldiers.
Moscow said its 205 released troops were brought to its ally Belarus, where they were receiving "psychological and medical assistance".
The exchanges remain one of the few remaining areas of cooperation between the two sides, at war since Russia ordered troops into its neighbor in February 2022.
The release was the "first stage of the 1,000 for 1,000 exchange" that had been brokered and previously announced by US President Donald Trump, Zelensky said.
Most of the freed Ukrainian troops had been in Russian captivity since 2022, including those who fought for Mariupol's steelworks Azovstal and at the Chernobyl nuclear power plant, which briefly fell to Moscow at the start of its invasion.
- Slimming hopes for peace -
Thursday's devastating attack on Kyiv -- the deadliest on the Ukrainian capital for months -- further hit already slim prospects for a breakthrough on ending the war.
Kyiv's allies accused Russia of mocking diplomatic efforts to end the conflict.
Moscow has shown no sign of backing down from its aims in Ukraine, demanding that Kyiv give up four eastern and southern regions that Russia claimed in 2022 to have annexed.
Fresh Russian attacks on Friday killed one person in the southern Zaporizhzhia region.
In Russia, Ukrainian overnight drone strikes on an apartment block in the city of Ryazan -- southwest of Moscow -- killed four people including a child, officials said.
Unverified social media videos showed plumes of smoke rising over Ryazan -- a city of around 500,000 -- and a high-rise apartment block with several blackened floors.
The Ukrainian army, which has launched retaliatory drone strikes throughout Moscow's offensive, said it had targeted an oil refinery.
Since Russia's invasion began in 2022, hundreds of thousands of people have died, millions have been forced to flee their homes and parts of eastern and southern Ukraine have been decimated by fighting.
Russia currently occupies around a fifth of Ukraine: the entirety of the Crimean peninsula, which it annexed in 2014, most of the eastern regions of Donetsk and Lugansk -- collectively referred to as the Donbas -- and large parts of the southern Zaporizhzhia and Kherson regions.
