MOSCOW - Russian and Ukrainian security services have foiled a plot to assassinate Vladimir Putin after next week's presidential election, Ukraine's SBU counter-intelligence agency said on Monday.

Russian Channel One television said Ukrainian special services in the Black Sea port of Odessa had held two men linked to a group seeking an Islamist state in Russia's North Caucasus.

"I can officially confirm that they were preparing an (assassination) attempt on Putin," said Marina Ostapenko, a spokeswoman for the SBU.

Ostapenko said two men were under arrest. One was seized in Odessa after being wounded in an explosion at an apartment in the city on Jan 4 which also killed another alleged plotter.

The second man, who was on the international wanted list, was arrested a month later after initially escaping, she said.

"We found him in an apartment and detained him without a single shot being fired on Feb 4," she said.

Some Russians reacted with skepticism, making clear on social network sites that they did not believe the report or suggesting the timing of the announcement was intended to attract sympathy for Putin before the March 4 election.

Opinion polls show Putin, a former KGB officer before he became president, will easily win the election and reclaim the post he held from 2000 until 2008.

But he faces a growing opposition protest movement and wants to secure outright victory on Sunday.

The appearance of broad electoral fraud in December parliamentary elections has stirred skepticism about Putin largely among liberals and nationalists in the cities of Moscow and St Petersburg. The Internet has been used to mobilize anti-Putin protests over the last three months.

Support boost

Putin's spokesman Dmitry Peskov confirmed the report to the ITAR-Tass News Agency, but refused to comment further. Russian and Ukrainian special services wouldn't comment.

The station said the source for its information was Russia's Federal Security Service, the main KGB successor agency dealing with domestic security. It was impossible to independently verify the claim.

Putin has counted the victory over Chechen rebels as one of the key achievements of his rule, and the report about the alleged plot is likely to further boost support.

Channel One said two of the alleged members of the group arrived in Ukraine from the United Arab Emirates via Turkey with instructions from Umarov, the top military leader for the Chechen rebels.

Pyanzin led the investigators to their liaison in Odessa, Adam Osmayev, a Chechen who previously had lived in London, the report said. The TV station showed some footage of Osmayev's arrest in Odessa with black-clad special troops bursting in and half-naked, bloodied Osmayev on his knees, his head bowed down.

Speaking to Channel One from custody in Ukraine, Osmayev described the group's mission: "Our goal was to go to Moscow and try to kill Prime Minister Putin ... Our deadline was after the Russian presidential election."

Several assassination attempts have been reported on Putin since he rose to power in 2000 but such reports have rarely made a big impact in Russia.

The chief insurgent group fighting for an Islamist state in the mountainous north Caucasus is known as the "Caucasus Emirate". It has carried out a chain of attacks including the suicide bombing of Russia's busiest airport last year that killed 36.

Reuters-AP