Ukrainian police said in a statement that a car that Serhiy Shefir was traveling in came under fire in the village of Lisnyky at about 10 a.m., with more than 10 bullets hitting the vehicle. The driver was injured.

A special police operation is underway to search for the perpetrators and police are appealing for information about the circumstances of the "assassination attempt on the lives of two Ukrainian citizens."

President Zelensky, who is in New York for the UN General Assembly, said he didn't know yet who was responsible for the attack but described it as sign of weakness to target one of his aides.

Zelensky said in a video posted on Facebook that he would be heading back to Ukraine after delivering his speech at the UN later Wednesday.

"Frankly, I don't know who's behind it yet," Zelensky said. "Sending me a message by shooting at my friend's car is weakness."

Shefir appeared later during a briefing at the country's Ministry of Internal Affairs.

From left to right, Volodymyr Zelensky, Oleksiy Honcharuk and Serhiy Shefir attend a meeting in Kiev in September 2019.

"All I can say for my part is that the attempt was made to intimidate the highest echelons of power. But our President is strong-willed, you don't intimidate him with anything. He chose the right path and is going his own way. The public is supporting him," Shefir said.

A politician from Zelensky's ruling party, David Arakhamia, told Ukrinform state news agency that Shefir was in a "state of shock" but not injured.

"I had a short conversation with him ... He says that he was shot at, but the driver was hit ... The car was shot with an automatic weapon, as far as I know. The driver received three gunshot wounds, he was hospitalized, " Arakhamia said.

Mykhailo Podoliak, an adviser to the head of the office of the President of Ukraine, told Ukrinform that the incident could not be seen as anything other than a "deliberate" attempt to "kill a key member of the team."

"It is obvious that this open, deliberate and extremely brutal attack with the use of automatic weapons cannot be qualified other than an attempt to demonstratively kill a key member of the team," Podoliak said.

A photo released by the Ukrainian Interior Ministry press office shows the bullet impacts on vehicle.

While authorities have not determined who is responsible or a motive, Podoliak said it could be connected to policies aimed at reducing the "traditional influence" of oligarchs. "I will say at once that we certainly associate this attack with an aggressive and even militant campaign against the active policy of the head of state," Podoliak added.

Zelensky vowed his government's response would be "strong" and said would continue his efforts to fight corruption and reform the country.

"The strength of our team will not be affected. The course that I have chosen with my team, to change, to clean up our economy, to fight against crime, and against big and powerful financial groups -- this does not affect that in any way. On the contrary ... the Ukrainian people have given me a mandate for changes," he said.

The Kremlin has dismissed allegations from a Ukrainian parliamentarian that the apparent assassination attempt possibly has "a Russian trace." Arakhamia, head of the ruling party's parliamentary faction, said he was "inclined to think that this is some 'hello"' message to our team."

Kremlin spokesman Dmitry Peskov said attempts to find a Russian connection are due to an "overly exalted emotional state" in Ukraine.

"Unfortunately for us, these days, no matter what happens in Ukraine, none of the active politicians is able to exclude the Russian trace," Peskov said.