Russia's destruction of an apartment building in the Ukrainian city of Dnipro has sparked widespread condemnation of Vladimir Putin.
The devastating missile strike on the block of flats on Saturday in the east of the country has claimed the lives of at least 35 people, while another 35 people are still missing.
Up to 75 survivors were injured by the strike. Dozens of people are feared dead, trapped under the rubble.
Former boxer Wladimir Klitschko, who joined the Ukrainian armed forces after Russia's invasion began last February and whose brother is mayor of Kyiv, tweeted an image of the aftermath of the devastating missile strike on Dnipro.
He wrote: "Russia is not only targeting Ukrainian civilians. It is also targeting the very principles of international law. It endangers the whole world. It’s time for action now."
While Russia has denied targeting civilians, some have pointed to the attack has being a clear indication of how Putin plans to wage his war.
Carl Bildt, the former Swedish prime minister and co-chair of the European Council on Foreign Relations, tweeted a video of the destroyed apartment building and wrote: "Putin was here."
Russian chess grandmaster and political activist Garry Kasparov tweeted in response to Klitshcko: "Russian tactics haven't changed since the carpet-bombing of Grozny and Aleppo.
"Cities reduced to dust, populations slaughtered and scattered. That is Putin's goal for Ukraine. And then what will be next for his need for escalation? Fight now, stop delaying, save lives."
Belgian MEP Guy Verhofstadt called for a full set of sanctions to be imposed on all western companies and individuals that deal with Russia in the wake of the Dnipro attack.
Watch: Death toll rises after Russian strike on Dnipro apartment block
Kaja Kallas, the prime minister of Estonia, called Russia a "terrorist state".
She wrote on Twitter: "With attacks on Dnipro and elsewhere in Ukraine, Russia has again proven it is a terrorist state.
"My call to allies and partners: let us ramp up our support. Ukraine needs weapons, including tanks and air defence. Russia must be held accountable for all crimes committed."
Russia's initial invasion plan was to take over the country in a matter of weeks, if not days. However, Putin has recently acknowledged that he is preparing his military for the long haul.
In December he warned the Russian population that they should be prepared for the "special military operation" – as he prefers to call the war – to be a "long process".
Some commentators are increasingly convinced Putin plans to copy the military playbook he used so effectively in Aleppo, Syria, this saw a years-long, indiscriminate bombing campaign that destroyed hospitals and schools and killed and maimed thousands upon thousands of civilians.
The next step in Ukraine could see a major new offensive launched by Putin in the spring, meaning Kyiv is locked in a "race" to build up its troops with support from the West.
On Saturday, Rishi Sunak confirmed the UK will provide tanks to Ukraine to help it “push Russian troops back”.
Sunak made the pledge during a call with president Volodymyr Zelenskyy, prior to Russia's missile strike on Dnipro.
Sunak offered Challenger 2 tanks and additional artillery systems as a sign of the UK’s “ambition to intensify our support to Ukraine”.
The UK is the first Western power to supply the Ukrainians with main battle tanks.
It comes after the US promised 50 Bradley tank-killing armoured vehicles in its biggest military assistance package to date for Ukraine.
Germany also announced it would supply about 40 Marder armoured personnel carriers and France promised wheeled AMX-10 RC tank destroyers.
Watch: Rishi Sunak says UK will provide tanks to Ukraine