The leader of Russian-backed separatists in the Donetsk region in eastern Ukraine has been killed in a blast at a cafe in Donetsk city, the separatist administration said Friday.
Alexander Zakharchenko, who led the self-proclaimed Donetsk People's Republic since 2014, died "as a result of a terrorist act," the separatist-run Donetsk News Agency reported.
Russia's state investigative committee said Friday it was treating the killing of Zakharchenko as an act of international terrorism. A criminal investigation into the killing has been opened, the committee said in its statement.
Russian President Vladimir Putin on Friday called Zakharchenko's killing a "dastardly" act that aimed to destabilize the fragile peace in the region.
However, Putin, in a statement issued by the Kremlin, did not accuse Ukraine of being behind the killing. Putin expressed his condolences to Zakharchenko's family.
Earlier, RIA news agency had said Russia's Foreign Ministry said it had every reason to believe Kiev was responsible for Zakharchenko's death.
Foreign Ministry spokeswoman Maria Zakharova said Zakharchenko's death showed that Kiev had decided to engage in a "bloody fight" and had passed up on its promises of seeking peace, RIA reported.
Russian-backed opposition fighters threw off Ukrainian central rule in an armed uprising after pro-Western leaders opposed by Moscow came to power in the Ukrainian capital, Kiev, in 2014.
Zakharchenko, a 42-year-old former coalmine electrician, became leader of the Donetsk Republic in November 2014. Other rebel leaders say he was handpicked for the role by Moscow. A vote held by separatists confirmed him in office.
The separatists have blamed Ukraine for previous attacks inside opposition-held territory.
The separatists have been dogged by infighting that has, on occasion, turned violent. Several past leaders of the separatists have fled the region, saying they feared for their lives after their comrades turned on them.