Prominent Russian war reporter Arkady Babchenko, who was shot dead in the stairwell of his building in Kiev on Tuesday, is the latest Kremlin critic to be murdered in Ukraine.
Here are other high-profile killings of those who have spoken out against the Kremlin in Russia's Western neighbour.
Former Russian MP and later Kremlin critic Denis Voronenkov was shot dead in broad daylight in Kiev last year.
Voronenkov used to be a federal lawmaker with the Communist Party but, after losing his seat in 2016, moved to Ukraine with his wife, Maria Maksakova, a well-known opera singer and a lawmaker for the ruling United Russia party, under a cloud of fraud allegations.
He became openly critical of Moscow's annexation of Crimea in 2014, testifying in a case against Ukraine's former pro-Russian president Viktor Yanukovych, who was ousted earlier that year.
The month before his death, he told Ukrainian media he had received repeated threats from the Russian security services, saying the situation in his homeland was "like Nazi Germany".
Kiev has blamed the Russian security services for the killing and has detained two suspected accomplices, both Ukrainians.
Voronenkov's bodyguard fatally wounded the gunman, who was a Ukrainian citizen and had fought in a volunteer battalion against pro-Russian separatists in the country's east. Kiev alleged he had been recruited by Russia's FSB security service.
Prosecutors also accused Maksakova's former partner Vladimir Tyurin of having ties to Russia's security services and being behind Voronenkov's killing.
Tyurin and two additional Ukrainian suspects are being sought by Kiev.
Amina Okuyeva, the doctor wife of Chechen volunteer soldier Adam Osmayev who was accused of plotting to murder Russian President Vladimir Putin, was killed last year in an attack that also wounded her husband.
The pair's car was hit by a hail of bullets as it was crossing a railway line in a village near Kiev.
Osmayev was accused by Moscow authorities of planning to kill Putin just weeks before the Russian leader's election to a third term in 2012.
He was held for two-and-a-half years in a Ukrainian prison but never extradited to Russia and was released soon after the 2014 pro-European uprising.
He and his wife then fought as volunteers alongside Ukrainian forces battling Russian-backed insurgents in the country's east.
Osmayev had already survived an assassination attempt in Kiev earlier in the year. The assailant was shot dead by Okuyeva on that occasion.
Her killing remains unsolved.
Independent journalist Pavel Sheremet was killed by a car bomb in 2016 while driving near his home in Kiev.
Sheremet had worked for Russian state TV but moved to live in Kiev in 2014 -- the year Moscow annexed Crimea -- over his critical views on the Kremlin's tough stance on Ukraine.
He had begun his career in his home country Belarus but left after confronting authoritarian President Alexander Lukashenko.
He founded the popular Belarussky Partizan opposition website after being detained and expelled from Belarus for his political attacks.
The reporter's murder remains unsolved.