MOSCOW — Aleksei A. Navalny, Russia’s leading opposition figure, was placed under house arrest on Friday and ordered not to use the Internet or telephone for two months, thus removing President Vladimir V. Putin’s fiercest critic from public life.

In his verdict, Judge Artur Karpov of Basmany Court in Moscow ruled that Mr. Navalny had violated the terms of a travel ban from a pending criminal case accusing him of defrauding a local branch of the cosmetics producer Yves Rocher.

The stiff restrictions in what is widely seen as a politically charged prosecution will effectively muzzle Mr. Navalny, the blogger and politician who has used social media to publicize mass demonstrations against the Kremlin and release damning accounts of corrupt practices in government bids. The most recent of those accounts asserted that billions of dollars probably were stolen in the preparations for the Sochi Olympics.

“Their only goal is to stop my political activities,” Mr. Navalny told Judge Karpov in front of a packed courtroom. “They want to stop me from coordinating our anticorruption investigations.”