Adam Osmayev, 36, blamed the attack on Russia after he survived and his 34-year-old wife Amina Okueyva was fatally shot in the head.
The second assassination bid on the pair this year follows the withdrawal of state protection guards, it was reported.
Osmayev, an ethnic Chechen, had been accused of a 2012 bid to blow up the Russian president’s motorcade in Moscow.
While growing up in Britain he had attended Wycliffe College near Stroud, Gloucestershire, before moving to Buckingham University.
Osmayev and Okuyeva, a trained sniper, both served as volunteers for the Ukrainian military in the fight against pro-Russian rebels. Osmayev was a battalion commander.
He was also linked with strong opposition to Putin’s crushing of rebels in his native Chechnya where his father had been a high ranking official.
The ambush that killed his wife occurred in Ukraine as they drove outside the capital Kiev.
An assassin hiding in bushes shot as they were close to a level crossing.
Osmayev said from the hospital where he was being treated for leg wounds: “I kept driving as long as I could but bullets got into the engine, too, and the car stopped.
“I tried to help Amina but she was wounded in her head”
He immediately blamed Russia for the attack as did other Ukrainian sources.
“It was an attempt on us both,” he said.
Asked if Moscow was behind it, he said: “Naturally.”
Anton Gerashchenko, an advisor to the Ukrainian interior minister, said: “Adam Osmaev was wounded but will live, I just spoke with him on the phone.
“As a result of the injuries she sustained, Amina died.”
He called her a Ukrainian “patriot”, adding: : “The best commemoration of her will be a just reprisal against all those who were involved in this horrible murder.”
He claimed the previous attempt was staged by Russian secret services.
The couple had survived an earlier assassination attempt in June when his Ukrainian wife used her Makarov handgun to shoot and wound an attacker, carrying a Glock pistol, posing as a French journalist.
Osmayev had been jailed in Ukraine for three years for illegal possession of explosives and forgery after the accusations that he had plotted to assassinate Putin.
After intervention by the European Court of Human Rights, Ukraine had refused to extradite him over the alleged plot.