MOSCOW (AP) — Prime Minister Vladimir Putin’s party saw its majority in Russia’s parliament weaken sharply, according to preliminary election results released today, a humiliating setback for the man who has steadily tightened his grip on the nation for nearly 12 years.

Some opposition politicians and election monitors said even a result of around 50 percent for Putin’s United Russia party was inflated because of vote fraud. Their claims were backed by European election observers, who pointed to procedural violations and serious indications of ballot stuffing after a campaign slanted in favor of United Russia.

“To me, this election was like a game in which only some players are allowed to compete,” Heidi Tagliavini, the head of the European mission, said at a news conference.

United Russia is still expected to retain its majority in the lower house and Putin is all but certain to win next March’s presidential election, but Sunday’s vote badly dented his carefully groomed image. It reflected a strong public frustration with the lack of political competition, ubiquitous official corruption and the gap between rich and poor.

With about 96 percent of precincts counted, United Russia was leading with 49.5 percent of the vote, Central Election Commission chief Vladimir Churov said. He predicted that it will get 238 of the Duma’s 450 seats, a sharp drop compared to the previous vote that landed the party a two-thirds majority in the State Duma, allowing it to change the constitution.

Final preliminary results were to be announced later today.