Voting has begun in Russia's parliamentary elections amid allegations of violations of election law.
The country's only independent election-monitoring group, Golos, has compiled 5300 complaints.
Its head, Lilya Shibanova, was held for several hours at Moscow's main airport after refusing to hand over her laptop.
Prime Minister Vladimir Putin has accused foreign countries of meddling in election preparations.
The Golos monitors, who are non-party political, are funded largely by the US and EU.
Russian MPs have questioned why the foreign-funded organisation - whose name means "voice" or "vote" - is allowed to monitor Russian elections.
On Friday, the group was fined the equivalent of $US1000 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 the politically dominant United Russia, chaired by Prime Minister Vladimir Putin.
Ms Shibanova said officials had taken her laptop on the pretext that it had illegal software, she said.
Seven parties have been allowed to field candidates for parliament this year - down from 11 in 2007.
Voting for representation in the country's 450-seat chamber takes place across Russia's nine time zones with polls closing at 1700GMT on Sunday.
The outgoing parliament is dominated by Mr Putin's party, United Russia, with seats also held by the Communist Party, the nationalist Liberal Democrats and the social-democratic Fair Russia.