The murder of east Ukraine's main separatist leader is a provocation that will undermine a Western-brokered peace agreement, Russian President Vladimir Putin's spokesman said on Saturday.
"This is no doubt a provocation," Kremlin spokesman Dmitry Peskov told reporters, Russian news agencies reported.
"(Alexander) 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.
The 42-year-old head of the self-proclaimed Donetsk People's Republic was killed in a bombing at a cafe in the rebel-controlled city of Donetsk on Friday, becoming the four-year conflict's most prominent victim from the Moscow-backed side.
Other Russian officials were also quick to stress that Zakharchenko's assassination was a huge blow to efforts to settle the Ukraine crisis.
"What happened today puts a big question mark over the entire process," Russian foreign ministry spokeswoman Maria Zakharova said in televised remarks late Friday.
Putin swiftly sent condolences on Friday, saying he expected to see the killers brought to justice.
In a letter published on the Kremlin website, Putin has praised Zakharchenko as "a true people's leader, a brave and resolute man".
Peskov said on Saturday that Putin had no current plans to meet the acting head of the self-proclaimed republic.
Zakharchenko -- who briefly worked as a mine electrician before going into business connected to the industry -- had led Russian-backed insurgents in the rebel region for the last four years.