Moscow: Russia's elections chief said Monday that voting by mail in the US presidential election had paved the way for massive voter fraud, echoing rhetoric from the campaign of Donald Trump.

Ella Pamfilova, the head of Russia's elections commission, said she had carefully studied mail-in voting in the United States and found the process vulnerable to fraud.

“For me, the conclusion is clear: this anachronism in its American form leaves massive scope for possible falsifications,” Pamfilova told the state-tun TASS news agency.

She cited the possibility of repeat voting, the unexplained loss of "unwanted" ballots, voting among people listed as deceased and a “lack of systemic control over the whole voting process.”

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Trump has refused to concede defeat to US President-elect Joe Biden and tried to sow doubt about the election results -- without providing evidence.

Trump in particular focused his criticism on mail-in ballots which surged this year and tilted heavily to Democrats.

Russia was accused of interfering in the 2016 US election to help get Trump elected, in the hope he would take a softer line with Moscow.

Biden is expected to take a tougher stand and during the campaign slammed Trump for having "embraced so many autocrats around the world, starting with (Russian President) Vladimir Putin".

Putin is one of the few leaders who has not yet congratulated Biden.