Ukraine's President Volodymyr Zelensky has said the death of Yevgeny Prigozhin – the Russian mercenary leader whose plane crashed weeks after he led a mutiny against Moscow's military leadership – shows what happens when people make deals with Russian leader Vladimir Putin.

As Ukraine's counteroffensive moves into a fourth month, with only modest gains to show so far, Zelensky told CNN's Fareed Zakaria he rejected suggestions it was time to negotiate peace with the Kremlin.

"When you want to have a compromise or a dialogue with somebody, you cannot do it with a liar," Volodymyr Zelensky said.

The Wagner leader's dramatic death, which followed a short-lived rebellion that threatened the authority of the Russian president, was a warning to be heeded, Zelensky suggested.

While the United States and other key Ukrainian allies continue to supply weapons to Kyiv, and stress that conditions to pursue a "just and durable" peace are not yet in place, a handful of world leaders, such as Brazil's Lula Da Silva, have put the onus on Ukraine to end the war.

As evidence for his position, Zelensky cited other countries which have been attacked by Russian soldiers and continue to be partially occupied by them.

"Did you see any compromise from Putin on other issues? With Georgia? With Moldova?" Zelensky asked rhetorically.

Ukraine has made incremental gains in the south amid fierce fighting with Russian troops, accounts from the front lines suggest.

Geolocated videos on Friday showed a wasteland of shell holes, abandoned trenches and wrecked military hardware in the area between Robotyne, Verbove and Novoprokopivka — a triangle of villages that hold the key for Ukrainians to getting closer to Tokmak, an important hub for Russian defenses.