Adam Osmayev, the 36-year-old leader of a battalion fighting pro-Russian rebels in Ukraine's east, was wounded Thursday in a dramatic exchange in which his wife returned fire and injured the attacker, police said.
Osmayev, an ethnic Chechen, and wife Amina Okuyeva were expecting to be interviewed by a man who said he was a French journalist from the Le Monde newspaper.
When they met in the city centre and got into a car, the so-called journalist took out a gun and shot Osmayev in the chest.
Osmayev's wife responded immediately by shooting the assailant four times with her own pistol.
Both injured men were hospitalised and in a stable condition on Friday with police saying the attacker would be able to testify.
Officers said that the attacker carried a Ukrainian passport in the name of Alexander Dakar.
Anton Gerashchenko, adviser to the minister of internal affairs, wrote on Facebook that the crime could have been "prepared in advance by a killer sent to Ukraine by Russian special services."
In Paris, however, Le Monde said that the alleged assailant did not work for it.
"Le Monde would like to make it clear that none of its journalists is currently in Ukraine," the French daily said in a statement.
It said the name of the fake journalist was Alex Werner, possibly also spelt Verner, according to Ukrainian investigators.
The newspaper said none of its journalists had that name and condemned any attempt to "illegally appropriate" its journalists' identities.
Osmayev spent years in prison in Ukraine after being accused in 2012 over a bizarre plot to assassinate Putin, then a presidential candidate, by bombing his motorcade.
The plot was reported on state television in Russia just days before the presidential elections. A second suspect Ilya Pyanzin, a citizen of Kazakhstan, was extradited to Russia and jailed for 10 years.
Osmayev was detained in the Ukrainian city of Odessa and made a confession that he later said was extracted under torture.
He spent almost three years in prison but was convicted only of illegal possession of explosives and was never extradited to Russia.
Osmayev was released soon after Ukraine's pro-European revolution in 2014 and at the beginning of the separatist conflict in the east of the country joined a volunteer battalion to oppose the pro-Russian rebels.
Osmayev, who was reportedly born in the Chechen capital of Grozny, does not have Ukrainian citizenship, Gerashchenko said.
The bold crime came after a former Russian MP wanted by Moscow for fraud was shot dead in broad daylight in the heart of the Ukrainian capital on March 23 in what Kiev branded an act of "state terrorism."
