Prime Minister Vladimir Putin's party suffered a drop in support in Russia's parliamentary election Sunday.

With more than 80 percent of the ballots counted, results show United Russia winning just over 50 percent of the vote, compared with 64 percent in 2007. The Communist Party was running a distant second with just under 20 percent

Russian analysts in recent weeks predicted a sharp decline in the party's popularity, with voters voicing discontent about the growing income gap between Russia's rich and poor, and allegations of official corruption.

In 2007, United Russia held a two-thirds majority in the State Duma (lower house of parliament), which allowed it to change the constitution unchallenged. The party is now fighting to keep its majority in parliament.

Earlier in the day, police detained more than 100 opposition activists during a demonstration in Moscow. Dozens more were detained in St. Petersburg.

Also Sunday, a leading independent Russian vote monitoring organization, Golos, told VOA that Russian police blocked some of its poll watchers from their monitoring posts around the nation.

Golos and the popular Russian opposition radio station Echo of Moscow (Ekho Moskvy) also said their websites were hacked, making them inaccessible. Several opposition news sites also were not working.

Golos says it has compiled more than 5,300 complaints of election law violations, and it accused the ruling party of complicity in most of them.

Last week, Mr. Putin, the current prime minister, formally accepted his party's nomination to return to the presidency – a post that analysts say he is certain to win. He announced his intentions in September, confirming a deal under which he would appoint current President Dmitry Medvedev as his prime minister.

The planned job swap has angered many in Russia, who said it would strengthen authoritarian rule and clear the way for Mr. Putin to become Russia's longest-serving leader since communist times.

If he regains the presidency, the 59-year-old Mr. Putin could serve two more 6-year terms and remain in power until 2024. He was first elected president in 2000.