A key separatist leader in eastern Ukraine has been killed in a blast at a coffee shop in Donetsk, according to rebels.

The explosion on Friday fatally wounded Alexander Zakharchenko, head of the self-declared Donetsk People’s Republic, which has been pushing for independence since 2014 after Russia’s annexation of the Crimean peninsula.

Russia accused Ukraine of assassinating the 42-year-old, but Kiev said it had nothing to do with the explosion and blamed separatist infighting.

Zakharchenko “received injuries incompatible with life as a result of an explosion in the centre of Donetsk”, the separatist administration said in a statement. It added that the blast also injured Alexander Timofeyev, the deputy prime minister of the self-proclaimed republic.

Russian President Vladimir Putin called the killing a “dastardly” crime aimed at destabilising a fragile regional peace.

“I expect that the organisers and executors of this crime will get the deserved punishment,” he said in a telegram of condolences released by the Kremlin.

“Zakharchenko was with his colleagues at the cafe when the bomb went off,” said Al Jazeera’s Rory Challands, reporting from the Russian capital, Moscow. “He is the only confirmed fatality so far from that explosion.”

Challands added Donetsk was in lockdown following the blast.

“Nobody is allowed in and nobody is allowed out,” he said.

Russia’s Investigative Committee, the state body that handles major crimes, said it was treating the killing as “an act of international terrorism”.

‘Bloody fight’

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 ceasefire has been in force since 2015, halting large-scale fighting, though there are still frequent outbreaks of shooting incidents on the front line between the separatists 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 on its promises of seeking peace, she said.

In Kiev, a spokeswoman for the state security service, Yelena Gitlyanskaya, dismissed Moscow’s accusations.

“According to our information, this was the result of internal fighting which has already been continuing for years between the terrorists and their Russian sponsors,” she said.

Michael Bociurkiw, a global affairs analyst and former spokesman for the Organization of Security and Co-operation in Europe (OSCE), said throwing blame at Ukraine “is a standard line out of the Russian playbook”.

“This looks like an internal operation because for the past few weeks and months, Zakharchenko has been critical of some of his colleagues and deputies in the so-called DPR parliament,” he told Al Jazeera in an interview from the Canadian town of Sidney, in British Colombia. “So, I think the writing was on the wall for him.”

A traffic policeman blocks a road near the cafe where Zakharchenko was killed [Alexander Ermochenko/Reuters]

Coalmine electrician to rebel leader

Zakharchenko, a former coal mine electrician, joined pro-Russian separatists in an armed uprising in Donetsk in 2014 and sold his business to help fund the movement.

He took the reins as the leader of the Donetsk Republic in November 2014 from a number of Russians, in a bid to show that Ukraine’s separatist movement wasn’t a Russian-led operation.

Other rebel leaders say he was handpicked for the role by Moscow. A vote held by separatists confirmed him in office.

Zakharchenko introduced Soviet-style military parades with tanks in Donetsk and usually wore military fatigues, despite his political role.

In his statement on Friday, Putin lauded Zakharchenko as “a true people’s leader, a brave and resolute person and a patriot”.

He proposed the creation of a new country called “Malorossia” or “Little Russia”, encompassing Ukraine, with its capital in Donetsk.

“I’ve met him as part of the OSCE, and the one thing about him is that he always had a lot of firepower around him and an unmistakably firm handshake as well,” said Bociurkiw.

In the past, he said had been the target of several assassination attempts, accusing Ukraine of trying to kill him in an explosion back in 2016.