Moscow (CNN) -- A plot to assassinate Russian Prime Minister Vladimir Putin has been foiled, Russia's state-run Channel One TV reported Monday, less than a week before presidential elections that Putin is expected to win.
Citing unnamed sources, the report said a group of plotters was arrested in the Ukrainian city of Odessa in early January and, after weeks of questioning, confessed to planning to kill the Russian leader.
The TV report included what it said was a confession by Adam Osmayev, a fixer associated with the two men who were seized in Odessa.
"Our final goal was to come to Moscow and try to organize an attempt on Prime Minister Putin," Osmayev said.
He said the plan involved using military-grade land mines to blow up vehicles.
Channel One showed video of what it said was the raid on Osmayev's apartment by armed security officers wearing black bulletproof vests and helmets. The video shows Osmayev, with red marks on his back and bloody bruises on his face, kneeling as officers demand his name.
Ukraine's domestic security agency, the SBU, uncovered the plot after an explosion at an apartment building in Odessa killed one of the plotters and injured another, Channel One said. The survivor tipped them off to Osmayev's involvement, the report said.
The plotter who was killed was allegedly willing to be a suicide bomber, and the mission was organized by Chechen militant leader Doku Umarov, Channel One reported.
CNN has not independently confirmed the existence of the plot, and a former British ambassador to Moscow expressed doubts about it.
"There was a similar alleged plot against him the election before last," Andrew Wood said. "That's pretty much (all) you need to know. It's suspiciously convenient."
Putin has dominated Russian politics for more than a decade, and his opponents accuse him of rigging parliamentary elections late last year.
International observers also said that the election was not free and fair, and protests of a size not seen in Russia in two decades followed the vote.
Wood said the protests may have encouraged the Kremlin to say there was a plot against Putin's life to build support for him.
"They've been taken aback by the degree of opposition," said Wood, who is now a Russia expert at Chatham House, a think tank in London.
"Even if he wins this election, which one must assume that he will, it won't necessarily mean that he has strong and durable support," he said.
Wood did not say outright that he did not believe there was really a plot to kill the prime minister.
"It's conceivable, but it seems improbable. Anything could be true. I can't say it's not true," he said.
Putin's spokesman Dmitry Peskov told the Russian news agency Itar-Tass that he confirmed the TV report but would not comment on it.
The Russian FSB declined to answer CNN questions about the alleged plot.
The announcement comes a week ahead of this Sunday's presidential election.
Putin handed over the presidency to ally Dmitry Medvedev in 2008, when he was barred from seeking a third consecutive term. After spending four years as prime minister, he announced in December that he would seek the presidency again.
Human rights groups say civil liberties and democratic freedoms have suffered during his rule.
But opponents took to the streets by the thousands after his United Russia party won a narrow majority in December parliamentary elections, which monitors from the Organization for Security and Cooperation in Europe said were "slanted in favor of the ruling party."
The leading opposition candidate in the March 3 vote is Communist Gennady Zyuganov.
Russia's third-richest man, billionaire New Jersey Nets owner Mikhail Prokhorov, and ultranationalist Vladimir Zhirinovsky are also running.
Critics of Putin's showed up in the thousands on Sunday in a show of strength ahead of the election. They attempted to complete a circuit of Moscow's 15-kilometer (9.3-mile) "Garden Ring" road but fell short.
The RIA Novosti news agency quoted police as saying 11,000 people turned out Sunday, far below the estimated 34,000 needed to complete the human chain.
CNN's Richard Allen Greene contributed to this report.