On May 4, passersby found Komarov in downtown Cherkasy, a city in eastern Ukraine, with severe head injuries and called an ambulance and the police, according to news reports.
He was taken to a local hospital, and has been in a coma after undergoing brain surgery on the same day; his condition has been described as "grave," according to those reports.
On the day of the attack, the Cherkasy police department issued a statementannouncing that it had opened an investigation. On May 5, the case was classified as attempted murder, according to news reports.
"We are appalled by the brutal assault on Vadym Komarov, which comes amid a range of threats faced by investigative reporters in Ukraine," said Gulnoza Said, CPJ Europe and Central Asia program coordinator. "Ukrainian authorities should leave no stone unturned in identifying the motive and bringing the assailants to justice."
Police did not specify whether they believed Komarov was targeted for his reporting. The Cherkasy regional police did not respond to CPJ's emailed request for comment.
Sergiy Tomilenko, head of the National Union of Journalists of Ukraine, a trade organization representing the country's staff and freelance journalists, told CPJ that Komarov is a well-known Cherkasy-based reporter and had been investigating official corruption in local sports schools prior to the incident.
On May 3, Komarov wrote on his Facebook page that he planned to publish information related to sports schools "in the coming days."
The journalist's most recent work includes a report on protests in prisons for the independent Ukrainian news website Dzvin, Tomilenko said.
Investigative journalists in Ukraine have recently faced surveillance, harassment, and assault from government and private entities, according to CPJ reporting.