Pro-Russian rebels in Ukraine confirmed that key separatist leader Alexander Zakharchenko was killed on Friday, adding that that several "Ukrainian operatives" were detained after the deadly blast.

Zakharchenko served as the president and head of government of the so-called "Donetsk People's Republic." The area is one of the two self-proclaimed rebel-controlled entities on Ukrainian territory, alongside the "Luhansk People's Republic."

What we know so far:

A blast hit a coffee shop in the city of Donetsk, killing Zakharchenko.

At least two other people were wounded, including the entity's "finance minister," Alexander Timofeev.

Rebel authorities claim they have several suspects in custody.

The killing of Zakharchenko "annuls" all efforts to end the Ukraine conflict, said Russian Duma speaker Vyacheslav Volodin.

Read more: Across the frontlines in Eastern Ukraine

Russia has 'all reasons to believe' Ukraine was behind the bombing

Moscow accused "the Kyiv war party" of staging terror attacks after the coffee shop blast in Donetsk.

"They are not fulfilling promises of peace, and as we see, they decided to move on to the bloody battle," said Russia's Foreign Ministry spokeswoman Maria Zakharova. She added that Moscow had "all reasons to believe" Kyiv was behind the attack.

Separatist leaders pledged a response, saying the blast was "an obvious act of aggression by Ukraine."

On Saturday, Russian President Vladimir Putin's spokesman said the murder was a provocation that will undermine a Western-brokered peace agreement.

"This is no doubt a provocation," Kremlin spokesman Dmitry Peskov told reporters, Russian news agencies reported.

"Zakharchenko's death will certainly lead to increased tensions in the region" and undermine the so-called Minsk agreements brokered by France and Germany in 2015, Peskov said.

Zakharchenko was a 'true people's leader'

Russian President Vladimir Putin offered his condolences to Zakharchenko's family, praising him as a "bold and resolute man" and a "true people's leader."

"The vile murder of Alexander Zakharchenko serves as yet another testimony that those who have chosen the way of terror, violence, intimidation do not want to pursue a peaceful, political solution of the conflict," Putin said in a statement.

The Russian president also addressed the residents of the rebel-controlled areas, saying that "Russia will always be with you."

Kyiv points finger at Moscow

Kyiv's intelligence agency SBU offered two versions of Zakharchenko's killing, hinting that Russia may be involved in the attack.

"We have reasons to believe that Zakharchenko's death could be the result of an internal struggle among the militants, mostly due to redistribution of business interests," said SBU chief Igor Guskov. "However, we also don't exclude the possibility that it was an attempt by Russian intelligence services to remove a disliked figure, which, according to out information, became superfluous and was bothering the Russians."

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Shaky ceasefire: The assassination of Zakharchenko threatens to reignite the conflict between the rebels and the security forces, which had been reduced to occasional shelling with virtually no large-scale skirmishes between the two sides. This week, the rebels and the government agreed to a truce to allow for students to attend classes at the beginning of the school year.

Read more: Ukraine separatist proclaim 'Little Russia' as new state

A look at the war in eastern Ukraine: Russian-speaking rebels rejected Kyiv rule in 2014, following the ouster of Russia-friendly Viktor Yanukovych and Russia's annexation of Crimea. The war has since claimed over 10,000 lives. Ukraine blames Moscow for orchestrating the rebellion and supplying the militants with weapons. Russia denies direct involvement, but admits there are Russian volunteers fighting alongside local forces. The conflict, alongside the takeover in Crimea, prompted a diplomatic ice age between Moscow and Western countries, with the US and EU imposing sanctions on Russia.

dj/kms (AP, Reuters, Interfax)

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