"Attacks against civilians and civilian infrastructure, wherever they occur, constitute clear violations of international law," said UN Secretary-General António Guterres in a written statement.
He called for an “immediate and unconditional ceasefire.”
US President Donald Trump is calling for an end to the "senseless killing".
"The president and his team have worked hard to end the war between Russia and Ukraine and he remains optimistic about reaching a final peace agreement," a Trump administration official told AFP in response to a question about the latest Russian attacks.
At least 20 people were killed in a wave of Russian drone and missile attacks on several Ukrainian cities overnight Thursday.
