Russia has been widely condemned after bombing cities across Ukraine, including rocket attacks on central Kiev for the first time.
The US said the brutal attacks had hit non-military targets, including a university and a children's playground, while continuing to promise military aid.
US President Joe Biden was one of several foreign leaders to speak to Ukrainian President Volodymyr Zelensky after the attacks, and he pledged to continue providing Ukraine with the support it needs to defend itself, including systems advanced air defence, the White House has announced, the BBC reported on Tuesday.
Biden said the attacks demonstrated the brutality of Putin's illegal war.
After the call, President Zelensky vowed to strengthen Ukraine's armed forces and make the battlefield even more painful for the enemy.
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China and India, which have not condemned the war, called for "a de-escalation".
Meanwhile, the head of the United Nations, Antonio Guterres, said he was "deeply shocked".
Russian President Vladimir Putin said the attacks were revenge for Saturday's blast on a key bridge linking Russia to Crimea.
Ukraine claims that 83 missiles were launched, of which more than 43 were shot down.
The deadly barrage included attacks in the cities of Lviv, Kharkiv, Dnipro and Zaporizhzhia.
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At least 14 people were killed and dozens more injured, officials said.
Several regions were left without electricity and water after the missiles hit energy infrastructure.
