Air raid sirens have been activated in the Ukrainian capital in connection with the explosions, and residents are being urged to seek shelter.
"The capital is under ballistic attack. Seek shelter!", writes Klitschko on Telegram.
According to Klitschko, at least one person has been killed and at least two others injured in last night's attack.
As of Wednesday night, at least seven people were killed in Russian attacks.
Russian Foreign Minister Sergei Lavrov said at a meeting with the UN Security Council on Wednesday that Moscow will not pause its war against Ukraine.
In early September, US President Donald Trump sent his envoys to both Kyiv and Moscow to try to breathe new life into negotiations to end Russia's war.
In recent days, Trump has called for an end to attacks on energy infrastructure. Ukraine has said it is willing to agree to this if Russia also stops its attacks.
