Russians are voting in polls that will decide the shape
of the lower house, or Duma, for the next five years.
There have been allegations of violations of election law, with Russia's only
independent monitoring group, Golos, logging 5,300 complaints.Its head was held at a Moscow airport after refusing to hand over her laptop.
Prime Minister Vladimir Putin, who leads the ruling United Russia party, has accused foreign powers of meddling in election preparations.
The Golos monitors, who are not affiliated with any party, are funded largely by the US and EU.
Duma members have questioned why the foreign-funded organisation - whose name means "voice" or "vote" - is allowed to monitor Russian elections.
Long voting day
Voting for representation in the country's 450-seat lower chamber takes
place across Russia's nine
time zones with polls closing at 17:00GMT on Sunday in Kaliningrad. As people in European Russia were going to bed, polls were opening in the far east.
In Vladivostok, sailors from Russia's Pacific fleet were among those queuing to vote.
Warrant Officer Nikolai Ponomaryov said he was voting for United Russia, because the party was supporting the armed forces.
In the far north, above the Arctic circle, voters braved temperatures of -26C to cast their ballots.
Polling stations have now opened in the capital, Moscow.
'Provocation'
On Friday, Golos was fined the equivalent of $1,000 (£641) by a Moscow court for violating a law that prohibits publication of election opinion research for five days before a vote.
Many of the allegations about electoral malpractice involved Mr Putin's
United Russia.Golos head Liliya Shibanova said officials had taken her laptop at Moscow airport on the pretext that it had illegal software.
"This is a provocation directed personally against me," she said, alleging that the authorities were trying to prevent her from travelling to the European parliament next week.
Seven parties have been allowed to field candidates for parliament this year - down from 11 in 2007.
The outgoing parliament, or State Duma, is dominated by Mr Putin's party, with seats also held by the Communist Party, the nationalist Liberal Democrats and the social-democratic Fair Russia.
A presidential poll will be held on 4 March, when Mr Putin will stand for election having served two previous terms in the post.
In a televised address on Friday, President Dmitry Medvedev insisted Russia's political parties enjoyed "free and equal competition" ahead of the election.
Without naming United Russia, he urged voters to choose "responsible politicians, who can help improve our people's living standards in practice, and who will be guided in their actions by the interests of voters and national interests".
