The leader of Russian-backed separatists in the Donetsk region in eastern Ukraine was killed on Friday in a blast at a cafe in Donetsk city, the separatist administration said.

Russia accused Ukraine of assassinating the separatist leader, Alexander Zakharchenko, to try to unleash a renewed war in eastern Ukraine, but Kiev said it had nothing to do with the blast and blamed separatist infighting.

Zakharchenko, who led the self-proclaimed Donetsk People's Republic since 2014, "received injuries incompatible with life as a result of an explosion in the center of Donetsk," the separatist administration said in a statement.

Russian-backed rebels 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.

A shaky internationally-brokered cease-fire has been in force since 2015, halting large-scale fighting, though there are still frequent outbreaks of shooting on the front line between the separatist and Ukrainian forces.

Russia's Foreign Ministry said it had every reason to believe Kiev was responsible for Zakharchenko's death, ministry spokeswoman Maria Zakharova said on the Rossiya-24 state television station.

Zakharchenko's death shows that Kiev has decided to engage in a "bloody fight" and has passed up on its promises of seeking peace, she said.