His comments came after Putin said that in his view, the whole of Ukraine was 'ours' and cautioned that advancing Russian forces could take the Ukrainian city of Sumy.
The Ukrainian leader also said that despite Putin's assertions at the St Petersburg Economic Forum, which ended on Friday, the Russian economy is declining and he would like to push it further down.
"The Russian economy is already crumbling. We will support this process even more," he said in Kiev.
"Ayatollah Putin can look at his friends in Iran to see where such regimes end up, and how far into decay they drive their countries."Â
Putin had reiterated Russia's claim to Ukraine at the forum and said he viewed Russians and Ukrainians as one people.
He also said Russia had a saying -"Where the foot of a Russian soldier steps, that is ours."
Ukraine's foreign minister Andrii Sybiha denounced Friday's statements as evidence of Russian "disdain" for US peace efforts and said Moscow was bent on seizing more territory and killing more Ukrainians.
Wherever a Russian soldier sets foot, "he brings along only death, destruction, and devastation," Sybiha said.
Russia currently controls about a fifth of Ukraine, including Crimea, more than 99 per cent of the Luhansk region, over 70 per cent of the Donetsk, Zaporizhzhia and Kherson regions, and fragments of the Kharkiv, Sumy and Dnipropetrovsk regions.
Kyiv and its Western allies say Moscow's claims to four Ukrainian regions and Crimea are illegal, and President Zelenskiy has repeatedly rejected the notion that Russians and Ukrainians are one people.
Putin said Moscow wanted Ukraine to accept the reality on the ground if there was to be a chance of peace - Russia's shorthand for the reality of Russia's control over a chunk of Ukrainian territory bigger than the US state of Virginia.
"Russia wants to wage war," Zelensky said in his nightly video address. The continued threats coming from Russia mean that "the pressure the world is applying isn't hurting them enough yet."
Zelenskiy said commanders had discussed action in Ukraine's northern Sumy region and that Russia had "various plans and intentions, completely mad as always. We are holding them back and eliminating these killers, defending our Sumy region."
Putin said Russian forces were carving out a buffer zone in the Sumy region in order to protect Russian territory.
