Russian state television said two suspects had been arrested in the Ukranian Black Sea resort of Odessa and who later confessed on air to acting on instructions from the Chechen warlord Doku Umarov to kill Putin after Sunday's elections.
A Chechen militant leader has claimed responsibility for the deadly twin blasts in Moscow metro two days ago which claimed 39 lives, a United States-based intelligence monitoring group reported on Wednesday.
The leader of an Islamist insurgency in Russia's North Caucasus region urged followers on Wednesday to use "maximum force" to prevent President Vladimir Putin staging the 2014 Winter Olympic Games in Sochi.
Two men said by Islamist militants to have carried out suicide attacks in south Russia appeared in a video donning explosive belts and warning Vladimir Putin to expect a "present" at the Sochi Winter Olympics from fighters following after them.
Intelligence agencies believe attacks by militants during the Sochi Winter Olympics are highly likely, but will probably be aimed at "softer" targets elsewhere in Russia, such as public transportation or other civilian venues, US and European officials said.
The Sochi Winter Olympics are meant to be Vladimir Putin's crowning achievement as Russian leader but are in danger of becoming a symbol of his country's problems.