Ukraine's President Volodymyr Zelensky has the approval rating of 57% of Ukrainians, a new poll showed, hours after US President Donald Trump said the head of state's approval rating was close to zero.

Calling for a presidential election in Ukraine, which is impossible under martial law, Trump said of Zelensky: "His approval rating is down to four percent approval."

A telephone survey of 1,000 people by the respected Kiev International Institute of Sociology showed that 57 percent of respondents trusted Zelensky, 37 percent said they did not trust him and the rest were undecided.

The poll found that confidence in Zelensky had risen by 5 percent since the last similar poll in December, despite Ukraine suffering military setbacks.

The institute said the Ukrainian president's approval rating had risen to 90 percent in March 2022 after Russia's invasion. Zelensky "retains a fairly high level of trust," the pollsters write.

Trump's stance echoes Russian President Vladimir Putin's claims that Zelensky "is not a legitimate president."

A Ukrainian law states that presidential elections are banned during martial law - introduced on 24 February 2022. In peacetime, Zelensky's term would have ended last May.

Critics point to a controversial clause in the Ukrainian constitution that says no president can serve more than five years, but can do so until a successor is elected.

Zelensky notes that holding elections is currently impossible as millions of Ukrainians live abroad or are fighting in the army, and the security risks are too high.

The authors of the study argue that "the majority of Ukrainian society continues to adhere to the view that elections should be held after the war".

It is unclear how Trump arrived at Zelensky's 4% approval rating figure.

Russian political analyst Fyodor Lukyanov told AFP in Moscow that this "figure is typical of Trump."

The US leader "pays no attention to boring things like facts and figures," Lukyanov added. | BGNES, AFP