* Moscow protest plans fizzle in face of police presence
* Dozens detained in St Petersburg
* Putin files candidacy papers in presidential bid
* Russia lashes out at U.S. criticism
(Adds demonstrations, police show of force, Gorbachev)
By Guy Faulconbridge and Steve Gutterman
MOSCOW, Dec 7 Plans for big new protests
against Vladimir Putin fizzled on Wednesday after a show of
force by Russian police who have detained more than 1,000 people
in a crackdown since a parliamentary election dismissed by
Kremlin foes as a fraud.
It was a setback for government opponents seeking to channel
public anger over the election, widely seen as slanted in favour
of Prime Minister Putin's ruling United Russia party, into a
powerful protest movement.
Putin pressed ahead with his bid to return to the presidency
next year, filing papers to register his candidacy, while former
Soviet leader Mikhail Gorbachev suggested the official results
of Sunday's vote were a "lie" and called for a new election.
A day after police dispersed protesters in central Moscow
and seized others before they could even reach the rally,
detaining more than 300, opposition activists had planned a new
demonstration at the same site 24 hours later.
But hundreds of helmeted riot police blocked off the square
after nightfall, pushing back reporters and shouting through
loudspeakers: "Respected citizens, please do not stop, walk on
your way so as not to hinder others."
Three youths emerged near a subway station entrance,
chanting: "We want free elections!". Riot police marched them
off to one of the dozens of police buses and truck that lined
the streets nearby.
In St Petersburg, about 250 people protested, most of them
youngsters, shouting "Shame!" Police detained about 70.
Kremlin opponents are trying to maintain momentum after
5,000 people turned out on Monday night for the largest
opposition protest in Moscow in years, demanding fair elections
and chanting "Russia without Putin!".
Police and Putin's spokesman have said unapproved protests
will be stopped. The Interior Ministry said some 50,000 officers
and 2,000 ministry troops remained in Moscow after the election.
A test of the drive to pressure Putin with street protests
will come on Saturday, when opponents hope for a big turnout at
a rally near the Kremlin.
Two protest leaders arrested after Monday's rally will still
be in jail then. A judge on Wednesday rejected appeals filed by
Alexei Navalny and Ilya Yashin against the 15-day jail terms
they received the previous day.
Monday's protest, fanned by fraud accusations that spread on
the Internet, underscored anger at United Russia and unhappiness
among some Russians at the prospect of Putin's almost certain
return to the Kremlin in a March presidential vote.
Voters bruised Putin in Sunday's election by sharply
reducing his party's majority in the State Duma lower house.
Undeterred, Putin filed candidacy papers for the March 4
presidential vote, submitting the documents in a brief, nearly
silent visit to the Central Election Commission headquarters.
Registration as a candidate is a formal step towards what
could be another 12 years in the top job for Putin, 59, who was
president from 2000 to 2008 and is now prime minister but
remains Russia's paramount leader.
Putin and President Dmitry Medvedev, the protege he tapped
as successor when the constitution barred him from a third
successive term in 2008, said in September they plan to swap
jobs next year, with Medvedev taking over as prime minister.
Putin remains Russia's most popular politician and is likely
to win a six-year presidential term, after which he could run
again, potentially serving until 2024.
But the sharp decline in support for his ruling party was a
sign of frustration with the political system he has put in
place, in which many Russians feel they have no influence.
United Russia received 49.4 percent of the votes in Sunday's
election and will have 238 seats in the 450-member Duma, down
from 315 now. Rival parties that won seats and the marginalised
politicians leading street protests say even that result was
inflated by fraud such as ballot-box stuffing.
GORBACHEV WANTS NEW ELECTIONS
"With each day, more Russians do not believe that the
declared results are honest," Gorbachev was quoted as saying by
Interfax news agency, adding that ignoring public opinion
discredited the authorities and destabilised the situation.
"And so I think it is necessary to annul the results of this
vote and announce new elections," he said.
Grigory Yavlinsky, whose liberal Yabloko party fell short of
the 5 percent of votes needed to win Duma seats, said those who
won seats should force a new election by refusing to take them.
"If you think that vote-rigging was substantial, then get
out of the State Duma ... then we can have new elections that
will pass off better," Yavlinsky told reporters.
The Communist Party will have 92 seats, the left-leaning
Just Russia will have 64 and the nationalist LDPR 56. Kremlin
critics say all three parties are part of a system managed by
the Kremlin and present no real threat to Putin's rule.
The election and the police crackdown has increased tension
between Russia and the West, already wary about Putin's planned
return to the Kremlin.
International observers said the campaign was slanted in
favour of United Russia. The United States and the European
Union voiced concern about the conduct of the election and the
treatment of protesters. Russia called the U.S. criticism
(Additional reporting by Thomas Grove, Darya Korsunskaya and
Jennifer Rankin, writing by Steve Gutterman, editing by Timothy