Moscow: Russian strongman Vladimir Putin on Wednesday refused to rule out a run-off in March presidential polls where he will seek a third Kremlin term but warned a second round risked causing instability.

"I understand that a second round run-off is possible, according to the current legislation," Russian news agencies quoted Putin as saying at a meeting with Russian election observers.

"I also understand -- and I think you do too -- that a run-off would unavoidably be linked to the continuation of a struggle and the destabilisation of the political situation."

"But there's nothing scary about it. I am ready for that, to work in the second round, if need be."

Prime Minister Putin is seeking to win back his old Kremlin job in March 4 presidential polls, despite an outburst of protests against his possible comeback.

He is wrestling with the worst legitimacy crisis of his 12-year rule after he announced his plan to seek a third Kremlin term in a job swap with incumbent President Dmitry Medvedev in September.

His approval ratings have dropped to an extent that he may not poll 50 per cent in the March 4 first round, forcing him to take part in a run-off three weeks later for the first time, a humiliating prospect for a leader who once enjoyed sky-high ratings.

 During a second round run-off, Putin would likely have to square off with veteran Communist leader Gennady Zyuganov, his nearest challenger in the presidential race.

Analysts say that if Putin, who still remains Russia's most popular politician, wins the polls in the run-off his victory would look more legitimate but a second round is fraught with unpredictable consequences.

Many opposition activists and ordinary Russians fear that the Kremlin will seek to falsify elections to let Putin win in the first round.

In 1996, Zyuganov forced the then president Boris Yeltsin into a run-off sending a scare across the country that Russia would go back to its Communist past.