The ruling United Russia party, which Putin founded, won 44.5 percent in Sunday's vote, an exit poll showed, slightly down on the last election. But it was still enough to preserve the dominance of Putin's allies in the Duma, or lower house of parliament.

Putin, speaking to United Russia campaign staff a few minutes after polling stations closed, said the win showed voters still trusted the leadership despite an economic slowdown made worse by Western sanctions over Ukraine.

Putin's aides are likely to use Sunday's result, which leaves United Russia by far the biggest party, as a springboard for his own campaign for re-election in 2018, though he has not yet confirmed that he will seek another term.

"We can say with certainty that the party has achieved a very good result; it's won," Putin said at the United Russia headquarters, where he arrived together with his ally Dmitry Medvedev, who is prime minister and the party's leader.

Alluding to the spluttering economy, which is forecast to shrink this year by at least 0.3 percent, Putin said: "We know that life is hard for people, there are lots of problems, lots of unresolved problems. Nevertheless, we have this result."

In the last election for the Duma, or lower house of parliament, in 2011, United Russia won 49 percent of the vote.

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There were some reports of voting irregularities. Reuters reporters at one polling station witnessed several people casting their ballot, then coming back later and voting again. Election chiefs said were was so far no evidence of large-scale cheating.

After the last election, anger at ballot-rigging prompted large protests in Moscow, and the Kremlin will be anxious to avoid a repetition of that.