Scores of people were killed or wounded when an aerial bomb hit a large store in the city of Kharkiv on Saturday afternoon, according to local officials.
The airstrike caused a huge fire to break out, with huge plumes of smoke seen filling the sky in social media footage.
Ukrainian president Volodymyr Zelenskyy said more than 200 people could have been inside the store.
A second bomb hit the city's central park, Kharkiv Mayor Ihor Terekhov said.
Zelenskyy called the airstrike “a manifestation of Russian madness", and appealed to Western countries to provide Ukraine with air defence systems.
“When we tell world leaders that Ukraine requires adequate air defence protection ... we are literally talking about how not to allow such terrorist strikes,” he said in a post on X.
"Only madmen like [Russian President Vladimir] Putin are capable of killing and terrorising people in this way," Zelenskyy added.
Kharkiv region is situated about 20 kilometres from the Russian border.
Moscow’s troops have in recent weeks captured villages in the area as part of a broad push, and analysts say they may be trying to get within artillery range of Kharkiv city.
Ukrainian authorities have evacuated more than 11,000 people from the region since the start of the offensive on 10 May.
Russia’s Kharkiv push appears to be a coordinated new offensive that includes testing Ukrainian defences in the Donetsk region further south, where Russia's Defense Ministry said Saturday that its forces had taken over the village of Arkhanhelske.
They have also launched incursions in the northern Sumy and Chernihiv regions.
Russian president Vladimir Putin has said the Kremlin’s army is attempting to create a “buffer zone” in the Kharkiv region to prevent Ukrainian cross-border attacks.
