Russia's President Dmitry Medvedev on Saturday harshly criticized officials in the ruling Kremlin-backed party for abusing their positions in order to win elections, saying the party must learn to win fairly.

The statement was Medvedev's strongest criticism yet of the United Russia party led by his predecessor and mentor, Prime Minister Vladimir Putin. United Russia controls parliament and serves as a power base for Putin, who has not ruled out a return to the presidency in 2012.

While unusually direct, Medvedev's statement appeared to be an attempt to respond to public criticism of the vote rather than mount a challenge to Putin.

Speaking before a major party meeting in St. Petersburg also attended by Putin, Medvedev accused some of United Russia's regional branches of using their dominance and official connections to shape the election results in their favor. He urged the party to "free itself of such people and shed such bad political habits."

"Elections must express the people's will in free competition between ideas and programs, but they turn into a different story when democratic procedures are mixed with administrative ones," he said, without elaborating.

Most top federal and regional officials in Russia are United Russia members, and the opposition has accused the party of using its leverage to rig the vote. Independent election observers and opposition parties, including the Communists, protested what they said were mass electoral violations during October's local elections, citing evidence of multiple voting and ballot stuffing.

Opposition candidates claim they were hindered from campaigning and some were denied places on the ballot.

Medvedev's statement contrasted with earlier remarks by Medvedev, who congratulated United Russia on winning a "convincing" victory while adding that claims of violations need to be investigated.

"It's necessary to modernize the party, make it more flexible and open," Medvedev said Saturday. "You must learn to win in open struggle."

"Democracy isn't for parties, either ruling or opposition ones, it's for the people," Medvedev said. He added on a softer note that United Russia is strong enough to retain its dominance without undermining democratic standards.

Putin didn't talk about the elections in his speech at Saturday's meeting, but he warned party members against seeing it as an "elite prestige club" for personal career goals.

Police detained 13 members of the National Bolsheviks, a banned leftist opposition group, as they were heading to the meeting to hand Medvedev a letter urging him to fire Putin, said Andrei Dmitriyev, a group leader. He said police accused them of crossing a street on a red light, which he denied.

Dmitriyev told The Associated Press the petition also voiced support for Medvedev's modernization drive, urged him to stop relying on United Russia and allow more political freedoms.

Since assuming the presidency last year, Medvedev has sought to cast himself as a more liberal-leaning politician than Putin, who rolled back many post-Soviet freedoms during his eight-year presidency.

Gleb Pavlovsky, a political strategist with close Kremlin connections, said that Medvedev's statement was a signal that he wants United Russia to more actively embrace his political goals. "There is a gap between positions of the president, the prime minister and the party," he said, adding that United Russia could eventually split into liberal and more conservative factions.

Most observers point out, however, that Medvedev's call for liberalization has been limited to words rather than actions, and see Putin as the man who continues to call the shots.

Medvedev's state-of-the-nation speech earlier this month focused on the need to shed Russia's dependence on oil and gas exports and ease an inflated state role in the economy. It was interpreted by some analysts as a sign of his desire to distance himself from Putin and shed his legacy.

But Putin made similar calls for easing dependence on raw materials in his speech at Saturday's meeting and hailed Medvedev's modernization goals.

Putin also took the credit for recent signs of economic recovery and pledged that his Cabinet would continue to support industries hit by the economic crisis, including the troubled carmaker AvtoVAZ.

He said that Russia's gross domestic product would fall by 8-8.5 percent this year, less than initially expected, and that the nation should regain the pre-crisis pace of growth in two or three years.