Members of the central electoral commission voted unanimously to reject her candidacy, citing "numerous violations" in the papers she had submitted in support of her bid.

Putin's critics said the decision showed that no one with genuine opposition views would be allowed to stand against him next March in the first presidential election since the start of the 22-month war. They see it as a fake process with only one possible outcome.

The Kremlin says Putin will win because he enjoys genuine support across society, with opinion poll ratings of around 80%.

Duntsova, 40, said on Telegram she would challenge the decision in the Supreme Court, calling it unjustified and undemocratic.

"With this political decision, we are deprived of the opportunity to have our own representative and express views that differ from the official aggressive discourse," she said.

In a separate development, Russian news outlets said Boris Nadezhdin, an opposition politician who has been critical of Putin and the war, was put forward as a candidate on Saturday by the centre-right Civic Initiative party. They said he planned to register with the electoral commission on Dec. 25.

'EVERYTHING AHEAD OF YOU'

The head of the electoral commission, Ella Pamfilova, offered words of consolation to Duntsova after her rejection.

"You are a young woman, you have everything ahead of you. Any minus can always be turned into a plus. Any experience is still an experience," Pamfilova said.

Screenshots posted by a telegram channel representing Duntsova showed documents with signatures that it said the commission had highlighted as inadmissible.

Duntsova appealed to veteran liberal politician Grigory Yavlinsky to let her run as a representative of his Yabloko party rather than as an independent candidate, which would allow her to submit a new application.

But Yavlinsky said in an interview on a YouTube channel that Yabloko was not planning to field a candidate and would not back Duntsova "because we don't know her".

When Duntsova said last month that she wanted to stand, commentators had variously described her as crazy, brave, or part of a Kremlin-scripted plan to create the appearance of competition.

"Any sane person taking this step would be afraid - but fear must not win," she told Reuters in an interview in November in which she called for the release of political prisoners and said Russians were "very tired" of the conflict in Ukraine.

BELARUS SCENARIO

Abbas Gallyamov, a former Kremlin speechwriter now labelled by the authorities as a "foreign agent", said Putin had not wanted to risk the same scenario as Alexander Lukashenko.

The Belarusian leader clung to power in 2020 only with the help of what the opposition and Western governments said was large-scale ballot rigging to enable him to claim victory over opposition candidate Sviatlana Tsikhanouskaya.

"The Tsikhanouskaya effect is absolutely possible, and in the Kremlin they understand that," Gallyamov wrote on Telegram.

Anastasia Burakova, a lawyer and rights activist also newly designated as a foreign agent, said the disqualification showed the authorities were determined that "not a single competitor who could cast a shadow on support for Putin and the war should be in the public field."

With Putin, 71, in full control of the levers of power, supporters and opponents alike say he will cruise to a new six-year term which, if he completes it, would make him Russia's longest serving ruler since the 18th century - outlasting all Soviet rulers including Josef Stalin.

His best-known opponent, Alexei Navalny, is serving prison sentences totalling more than 30 years and his supporters say they do not even know where he is, after they were told he had been moved from his previous penal colony earlier this month. Lawyers last had access to him on Dec. 6.

One of the nominal opposition parties in parliament, the A Just Russia - For Truth party, said on Saturday it would support Putin at the election, state news agency RIA reported.

Meanwhile the Communist Party, which has finished a distant second to Putin at every election since 2000, named 75-year-old Nikolai Kharitonov as its candidate.

Kharitonov stood previously in 2004 and won 14% of the vote to Putin's 71%. TASS news agency quoted him as saying he would not find fault with the Kremlin leader.

"He is responsible for his own cycle of work, why would I criticise him?" Kharitonov said.