MOSCOW, Feb. 27 - The security services of Russia and Ukraine report foiling a plan to assassinate Russian Prime Minister Vladimir Putin that was organized by an underground movement in the North Caucasus region, Russian state television reported Monday.

The report came less than a week before Russians go to the polls to vote on whether Putin should reclaim the presidency. Protests by tens of thousands of demonstrators, most recently in Moscow on Sunday, accuse officials loyal to Putin of cheating in parliamentary elections in early December. Nevertheless, he is expected to defeat his four opponents in the first ballot.

Some observers questioned reports of an assassination plot, suggesting it was either entirely fabricated or that the announcement of a real plot was made at a time when it could benefit Putin's campaign.

Russia's main state television channel reported that Ukrainian authorities arrested a Russian after a Jan. 4 explosion in an apartment in Odessa. One person died in the explosion, it said.

The survivor provided information leading to the arrest early this month of a second person, who was identified as Adam Osmayev, the TV report said.

In a video provided by Ukrainian authorities, a man with a bruised face who was identified as Osmayev said the group was planning to kill Putin sometime after Sunday's election, using antitank mines.

"The final goal was to come to Moscow and try and carry out an attempt on Premier Putin's life," he said. "The security service is not omnipowerful; it can't control all the cars, all the pedestrians in the street."

The report said that Osmayev's laptop, which was seized in the raid, contained several video recordings of Putin's motorcade route in and near Moscow, made from different vantage points. It said that information provided by Ukraine helped the Russians find a cache of plastic explosives and detonators buried near one of Moscow's major thoroughfares, Kutuzovsky Prospekt.

Putin's spokesman, Dmitry Peskov, confirmed to the Itar-Tass news agency that an attempt on his boss' life was prevented, but he refused to elaborate.

Putin, who has been prime minister since 2008, was first elected president in 2000 and quickly gained popularity by launching a fierce military campaign to regain control of the North Caucasus republic of Chechnya. But violence continues in the region's patchwork of ethnic republics, and over the years Chechen groups have claimed responsibility for a series of terrorist attacks in Russia.

Russian news reports identified Osmayev as a Chechen. The television report said he had arrived in Ukraine from the United Arab Emirates, that he had lived in London, and that he had received his instructions from representatives of Chechen insurgent leader Doku Umarov.

Some political experts called the reports of a plot little more than a publicity stunt.

"Putin seems oblivious to the fact that the country has changed in the last 12 years and people are not going to come out and protect the nation's leader with their bodies in an imaginary war," said Andrei Piontkovsky, a senior researcher at Moscow's Systems Analysis Institute.

But Sergei Markov, vice president of the Moscow-based Plekhanov Russian University of Economics, said the Kremlin may have taken advantage of information about a real plot to help Putin's campaign.

"It is a fact that Putin has always been the primary target for various terrorist groups, but until now the information about previous attempts on his life has been kept from the public," Markov said. "I think this time, given the decisive week of the campaign, they must have decided that it makes no sense to keep this important news from the public." (om/ez)