The authoritarian government of Belarus blocked access to Facebook, Twitter and a major Russian social networking site on Sunday  in an attempt to prevent opposition protests on a national holiday. Thousands of police and special forces were deployed in the center of Minsk, the capital.

The respected rights group Vesna said the government also detained dozens of opposition activists, including Stanislav Shushkevich, Belarus' first post-Soviet leader. Many other activists were called in by the KGB and warned not to protest, Vesna spokesman Valentin Stefanovich said.

The government is trying to contain swelling public discontent as Belarus suffers its worst financial crisis since the fall of the Soviet Union. President Alexander Lukashenko said on Sunday that "an escalation of information intervention is under way" as part of plans drawn up in "the capitals of separate countries" to bring about a popular revolution.

"We understand that the goal of these attacks is to sow uncertainty and alarm, to destroy social harmony, and in the end to bring us to our knees and bring to naught the achievements of our independence," Lukashenko said in opening a military parade on Independence Day, the anniversary of the end of Nazi occupation in 1944. He wore a military uniform, as did his 6-year-old son.

Belarus is under pressure from Russia and the West. Moscow has been pushing for greater control over the Belarusian economy in exchange for loans to help Lukashenko's government weather the financial turmoil, while the European Union has threatened to expand sanctions imposed on Lukashenko as punishment for his crackdown on the opposition.

For the first time, Russian troops took part in the annual military parade. Russian state television, which broadcasts in Belarus, has supported the Belarusian protesters by showing their rough treatment at the hands of police.

A new opposition group called "Revolution by Social Networks" has held a series of Internet-organized rallies in about 30 cities and towns. The rallies have drawn thousands of protesters, who carry no signs and walk silently through the streets clapping in unison.