At the end of a week of cyberattacks on popular, freewheeling Russian Web sites, which bloggers have blamed on shadowy government agencies, a top official with the federal security service on Friday proposed a ban on Skype, Gmail and Hotmail here because their use is “uncontrolled.”

An adviser to President Dmitry Medvedev, whose blog has been disrupted, was quick to criticize the proposal, and the communications minister, Igor Shchyogolev, ruled out the idea. But a spokesman for Prime Minister Vladimir Putin said it was worth studying and called the FSB’s proposal “quite well-reasoned.”

The foreign e-mail and communications Web services use encryption technology that makes them inaccessible to the security agency, said Alexander Andreyechkin, head of the FSB’s information and special communication center. That, he said, represents a threat to national security.

The Internet in Russia is a raucous and — so far — unfettered gathering place. Denial-of-service attacks have targeted LiveJournal sites and that of Novaya Gazeta, Russia’s most outspoken newspaper. Bloggers say the attacks are an effort to bring the Web here under control, a suspicion heightened by Andreyechkin’s remarks.

Medvedev is a big fan of the Internet. His LiveJournal blog was attacked shortly after he ordered government officials to give up their seats on the boards of state-owned enterprises.