Ukrainian security services have thwarted a plot to kill Russian PM Vladimir Putin, Russian officials say.
Two suspects were detained in the Ukrainian port of Odessa, Russia's state-owned Channel One TV reports.
The arrested men were both shown on TV admitting their involvement in the plot, after an explosion at a flat in January in which one suspect died.
A Ukrainian official confirmed to Reuters news agency the arrests were linked to a plot to kill Mr Putin.
When contacted earlier by the BBC, the spokeswoman had initially refused to corroborate the Russian TV report that linked the detention of two men to a conspiracy.
The Russian prime minister's press secretary, Dmitry Peskov, told the BBC "this was absolutely a plot to kill the prime minister."
The attack was to happen after next Sunday's presidential vote, the report said.
Mr Putin is expected to win the election and get a third term as president.
The BBC's Daniel Sandford in Moscow said the two men were both shown on Russian TV, one being interrogated and the other giving an interview.
In the footage, both admit plotting to attack Mr Putin. One, identified by Ria Novosti as Ilya Pyanzin, said he had been hired by Chechen militant leader Doku Umarov to carry out the killing and also by Ruslan Madayev, the suspect who died in the Odessa explosion.
The other suspect was named by Channel One as Adam Osmayev, said to have been on an international wanted list since 2007.
The plotters were planning to plant mines on Kutuzovsky Avenue in Moscow, used by Mr Putin on a daily basis, the report said.
Russian media report that Mr Pyanzin was arrested in the Odessa flat where the explosion happened. He told police that he and Madayev had flown to Ukraine from the United Arab Emirates via Turkey, with precise instructions from representatives of Doku Umarov.
According to the reports, details of the plot were found on laptops in the flat, along with a video showing Mr Putin's motorcade.
Mr Osmayev was reported to be the local fixer in Odessa and the instructor for the plotters, and had lived for a long time in London.