Russian opposition politicians and independent monitors Golos cried foul before the polls closed, alleging numerous instances of electoral fraud.

In Moscow, the city election commission chairman said foreign observers had not reported any abuses. Voting was proceeding "calmly and according to schedule", said Vladimir Churov, chairman of the Central Electoral Commission.

This followed accusations - denied by the Kremlin - that skewed media coverage, intimidation of opposition parties and the liberal use of government resources to promote United Russia had made the contest one-sided even before polls opened.

"These are the dirtiest, most irresponsible elections," Communist Party leader Gennady Zyuganov said. "... They have thought up at least 15 ways to entrap and betray voters".

Former world chess champion and opposition icon Garry Kasparov denounced the election after intentionally spoiling his ballot paper at a snowbound central Moscow polling station.

"They are not just rigging the vote, they are raping the whole electoral system," Mr Kasparov said. "These elections are a reminder of Soviet elections when there was no choice." Mr Kasparov has little popular support inside Russia.