Russian-backed separatists in eastern Ukraine are set to hold elections in two self-proclaimed republics on Sunday, in an apparent bid to cement their split from the rest of the country.

The elections in the Donetsk and Lugansk "People's Republics", which have been outside of Kiev's control since 2014, have been strongly condemned by Kiev and the West.

"While Ukraine takes positive steps to promote peace, Russia is stoking conflict by staging sham 'elections'," the US embassy in Kiev wrote on Twitter Wednesday.

It called on residents of eastern Ukraine to boycott the polls.

Brussels earlier said the so-called presidential and parliamentary polls were contrary to a 2015 agreement aimed at settling the conflict.

"We expect Russia in particular to make full use of its influence on the separatists in this regard," the EU said in a statement in September.

Eight European countries also condemned the "illegitimate" elections in a declaration at the United Nations last month, urging Russia to prevent them from going ahead.

But Moscow has rejected the appeals, insisting the vote has "nothing to do" with the 2015 Minsk peace accord.

– 'Power vacuum' –

Residents of the region decided unilaterally to hold the elections, Russian foreign ministry spokeswoman Maria Zakharova said in October.

She said people there were living with "permanent threats of the use of force by Ukrainian authorities."

"The November 11 elections are dictated by the need to fill the power vacuum after the death of Alexander Zakharchenko," she said, referring to a separatist leader who was killed in a bombing at a Donetsk cafe in August.

Denis Pushilin, a former negotiator with Kiev, is now acting leader of the self-proclaimed Donetsk republic.

Meanwhile Leonid Pasechnik, the 48-year-old former regional chief of the Ukrainian security service, is acting leader of the neighbouring republic of Lugansk, also unrecognised internationally.

"Moscow has decided that the legitimisation of new leaders outweighs criticism by the West," Alexei Makarkin of the Moscow-based Center for Political Technologies told AFP.

The conflict between Ukrainian government forces and the separatists broke out in April 2014, shortly after Russia's annexation of the Crimean peninsula, and has since claimed more than 10,000 lives.

Ukraine and the West accuse Moscow of militarily supporting separatists, claims that Russia denies despite overwhelming evidence.

The polls are also a way for the separatists to strengthen their grip on nearly three percent of the Ukrainian mainland, political analyst Volodymyr Fesenko said.

"If the elections were postponed, one could imagine these territories could come back under the control of the Ukrainian authorities one day," but that is far from being the case, Ukraine-based Fesenko told AFP.

– No more camouflage –

While several candidates are running in each of the two regions, the current acting leaders are almost certain to prevail.

Pushilin was last month received in Moscow by President Vladimir Putin's influential advisor Vladislav Surkov, a Kremlin negotiator on Ukraine, Russian media reported.

"Moscow does not even bother to conceal that it is behind the election campaign in Donbass and that its winner is determined in advance," the Moscow-based Carnegie centre said in a note.

"Zakharchenko was not a totally independent figure, but Pushilin is being controlled even more" by the Kremlin, it added.

Unlike his predecessor, who was known for his belligerent remarks and loved strutting in camouflage uniform, Pushilin wears a formal suit in public rather than military attire.

His election posters in Donetsk promise "a peaceful republic for peaceful citizens".

Other posters encourage residents to vote for a region "with a Russian heart", though the campaign has largely focused on social rather than military issues.

The last separatist elections were held in late 2014 despite protests from the West and Kiev, which did not recognise their results.