Russian customs officers held the director of an independent election watchdog for 12 hours at a Moscow airport on Saturday and seized her laptop computer in what the group said was an attempt to stop it monitoring Sunday's parliamentary election.

Liliya Shibanova, executive director of Western-funded group Golos, was detained at Sheremetyevo airport after returning from abroad for the election, which Vladimir Putin's United Russia party is likely to win with a reduced majority.

The pressure on Golos and its leaders (is) an attempt to block their activities involving independent public monitoring of the election, said a lawyer for Golos, Ramid Akhmetgaliyev.

Campaigning ended on Friday but election posters were allowed on Saturday far away from polling stations if they had been posted earlier. Moscow neighbourhoods were dotted with United Russia posters, but other parties' posters had gone.

Opposition parties say they expect voting irregularities on Sunday as part of efforts to boost United Russia's result, and complain the ruling party had more air time during the campaign.

Speaking to reporters after she surrendered her computer and let go, Shibanova said she had been told she allegedly had very dangerous software on her laptop.

A Moscow court ruled late on Friday that Golos had violated a ban on the publication of opinion poll results within five days of the election to the State Duma lower house.

A leading expert with Golos, Alexander Kynev, said Shibanova's detention and the court case amounted to a coordinated operation against the group and added: I am convinced that these are actions of government authorities.

Golos and its lawyers said they would appeal against the court decision, which came with a 30,000-rouble ($970) fine. They said Golos had published allegations of campaign violations, not opinion poll results.

Prime Minister Putin has accused foreign countries of meddling in the preparations for the election -- and for a March presidential vote he is expected to win -- by funding organisations in Russia.

The U.S. government issued a statement on Friday condemning the court ruling against Golos and what appears to be a pattern of harassment directed against this organization.

Russian lawmakers had earlier objected to Golos' foreign financing and urged it to stop vote monitoring.

Golos, a non-profit organisation, has a hotline for electoral violation allegations and an interactive map showing more than 5,500 reported violations linked to Sunday's vote.

It acknowledges it is funded from Europe and the United States, saying this helps it remain objective.

PUTIN SAYS WEST MEDDLING

During his 2000-2008 presidency, Putin repeatedly accused the West of seeking to weaken Russia and of meddling in its affairs, including by funding non-governmental organisations meant to strengthen democracy.

Formally launching his bid to return to the Kremlin next year by accepting United Russia's nomination at a party congress last Sunday, Putin reiterated these accusations.

He said representatives of some foreign countries are gathering those they are paying money to, so-called grant recipients, to instruct them and assign work in order to influence the election campaign in our country themselves.

He said any such activity was a wasted effort because Russians would reject foreign-funded politicians.

Russia's NTV television broadcast a film on Friday that portrayed Golos as a dishonest group working for U.S. cash and alleged that the Swedish embassy in Moscow had been teaching students to use social networks to organise mass protests.

The Swedish embassy issued a statement rejecting the allegations and dismissing suggestions one of its staff had been spying.

Critics in Russia and the West accuse Putin of curtailing democracy through a series of electoral reforms during his presidency, which coincided with an oil-fueled economic boom.

His announcement in September of plans to swap jobs with President Dmitry Medevedev upset some Russians who saw it as a back-room deal agreed with no regard for voters. Putin, 59, could be in power until 2024 if he wins two more terms.

If United Russia, which has dominated the State Duma lower house since 2003, does not retain its two-thirds majority, the biggest gainers could be the Communist Party, which is likely to remain the second biggest force. Vladimir Zhirinovsky's nationalist LDPR also hopes to gain votes from United Russia.

Medvedev, who is leading United Russia into the election, also criticised the West on Saturday, urging Russia's chief prosecutor to study ways to bring to justice foreigners who abuse children they adopted in Russia.

Russia's children's rights commissioner, Pavel Astakhov, said on Friday the United States had inexcusably failed to inform Moscow for years about the 2005 death of a Russian-born toddler adopted by an American couple.

(Additional reporting by Gleb Bryanski and Maria Tsvetkova, Editing by Timothy Heritage)