Ukraine's President Volodymyr Zelensky on Wednesday promised a "strong response" after gunmen opened fire on a car carrying his senior aide, in what officials said was retaliation for a push to rein in oligarchs.

Sergiy Shefir, a 57-year-old former scriptwriter and longtime associate of comedian-turned-politician Zelensky, was reported to have escaped without serious injury.

"Saying 'hello' to me by shooting out of the forest at my friend's car is weak," Zelensky said in a video statement from New York.

"The response will be strong."

Zelensky, who is in New York for the UN General Assembly, said it was not yet known who was behind the attack.

But he said: "This does not affect the course that I have chosen with my team -- towards changes, towards de-shadowing our economy, towards fighting criminals and large, influential financial groups".

Shefir called the attempt on his life an attempt to "intimidate" the presidency.

Police said they were considering possible motives.

Shefir may have been targeted for his work, or as part of a bid to pressure Ukraine's top leadership or destabilise "the political situation in our country," Igor Klymenko, head of the national police, told reporters.

An adviser to the interior minister, Anton Herashchenko, said on Facebook that the attack took place around 10 am (0700 GMT) on Wednesday near the village of Lisnyky south of the capital Kiev.

He said Shefir's driver was "seriously injured" and that police had launched a special operation in the area.

"Unidentified individuals fired about 10 shots from a 7.62 calibre automatic weapon," Ukraine's Prosecutor General Iryna Venediktova said on Facebook.

She said the authorities had opened an attempted murder investigation.

Photos published by officials showed a black Audi with bullet holes along its hood and on the driver-side door.

- 'Shadowy oligarchs' -

Official reports did not say whether Shefir was injured, but a lawmaker representing Zelensky's "Servant of the People" party said he was fine.

"I briefly spoke to him, everything is fine, he is alive and well," Davyd Arakhamia was quoted by Russia's RIA Novosti news agency as saying.

He said police had taken Shefir to a "safe" location.

Another aide in Zelensky's office, Mykhailo Podolyak, told the Interfax-Ukraine news agency the attack was in response to "politics directed at limiting the traditional influence of shadowy oligarchs.”