By Alissa de Carbonnel
MOSCOW (Reuters) - Russian opposition leaders said on Friday that unusually cold weather threatened to cut numbers at a protest against Prime Minister Vladimir Putin's 12-year rule planned for Saturday.
The march "For Honest Elections" will vie for airtime on state-owned television with pro-Putin rallies also set to take place in Moscow where temperatures are forecast to fall to minus 13 degrees Celsius (8.6 degrees Fahrenheit).
Galvanized by widespread allegations that Putin's party cheated at December parliamentary polls, tens of thousands of Russians marched in rallies in Moscow on December 10 and December 24.
Protesters want a re-run of the polls, a probe into allegations of voting fraud, electoral reforms and the release jailed tycoon Mikhail Khodorkovsky among others the opposition call political prisoners.
Saturday's demonstration will test the opposition's ability to keep up pressure on Putin, set for all-but certain victory in a presidential election on March 4, to meet their main demands.
"I have the feeling that every degree colder it gets, we lose 5,000 people," said liberal politician Boris Nemtsov, an organizer of the protest who served in government under President Boris Yeltsin.
Speaking at a news conference with fellow organizers, he voiced their advice that protesters to dress warmly. "The main thing is for people not to catch pneumonia... Three hours in the cold is a serious thing."
Journalist and fellow organizer Sergei Parkhomenko estimated 70,000 people would join the march.
More than 27,400 have signed up on Facebook alone for Saturday's march.
Protesters traded advice on social networking sites on how best to stay warm, and one posted photographs posing in the snow in a turquoise bikini holding the sign: "The cold isn't scary."
Putin has promised token political reforms and has mocked the demonstrators, saying they lack leadership and goals and comparing the white ribbon symbol of the protests to condoms.
He has also suggested protest are funded by foreign governments, a claim the opposition denies.
Videos circulated online advertising rival rallies on Saturday, painting the opposition march as a Western-sponsored plot to seed revolution and political chaos in Russia, and echoing warnings by top officials not only to watch out for frostbite but also raising the specter of revolution.
"Real Russian patriots should stay at home and make babies... not loiter at demonstrations," Deputy Prime Minister Dmitry Rogozin was quoted as saying by state RIA news agency.
Russia's public health watchdog head Gennady Onishchenko told Muscovites to stay home to beat the cold and "find another way to build a happier state," Interfax reported.
Organizers of pro-government rallies made no secret these are specifically planned to compete with the opposition march. Denounced by the opposition as a Kremlin-funded farce, they are dubbed the "Anti-Orange Rally," referring to Ukraine's 2005 Orange revolution, when Moscow has said Western-funded youth activists helped topple a pro-Russian government.
Separately, Putin said he shared the views of people who planned to participate in the pro-Kremlin rally at Poklonnaya Gora, a district in western Moscow.
"People who openly assert their anti-orangist position will walk out at Poklonnaya Gora (on Saturday)," he was quoted by Interfax as saying. "I am thankful to them and share their views."
Advertisements on online forums such as Massovki.ru offered to pay participants 1,000 roubles ($33), and Russian media reported that teachers and workers in state companies were being coerced into attending the pro-Kremlin rally.
Putin said he disapproved of administrative pressure being put on public servants and state company employees allegedly forced to attend the pro-government rally by their employers.
"There is absolutely nothing good about it," he said. "But exaggerating the same fact of use of (such pressure)... would not be right either."
(Additional reporting by Nastassia Astrasheuskaya and Alexei Anishchuk; Editing by Louise Ireland)