— Russia’s shrinking space for freedom of expression on the Internet is set to constrict further Friday, as tough regulations go into effect that will give Russian authorities powerful oversight over the country’s most-read online personalities, including opposition bloggers and politicians.

The restrictions come as some of Russia’s most prominent independent online news Web sites have been blocked or gutted in recent months, and at a crucial juncture in the Ukrainian conflict, which has raised tensions between Russia and the West to levels not seen since the Cold War. The Internet in Russia had long been a largely uncensored arena even as the nation’s television stations and newspapers toed an ­ever-stricter Kremlin line. The new regulations, bloggers and activists say, will encourage online self-censorship and will create new risks for those who advocate contrarian viewpoints.

The set of regulations coming into effect Friday is known here as the “blogger law” because it requires any person whose online presence draws more than 3,000 daily readers to register, disclose personal information and submit to the same regulations as mass media. Critics — including some pro-Kremlin lawmakers — say the rules are confusing, poorly written and hard to enforce consistently. But the end effect is to put large swaths of Russia’s prominent online personalities in theoretical violation of the law at all times, risking fines and other harassment whenever authorities decide to crack down, critics say.

Starting Friday, “every blogger might face a threat of criminal prosecution,” said Oleg Kozyrev, a prominent opposition blogger, who said he does not intend to register his Web site.

The new regulations come at a particularly tense moment in the Ukraine-Russia conflict, with Russian troops again massing at the border with Ukraine. Two weeks after Malaysia Airlines Flight 17 was shot down over ­rebel-held territory in eastern Ukraine, Russian television networks are covering the conflict far differently from their Western counterparts. Most have concluded that Ukrainian forces fired the missile that killed all 298 people aboard, bolstering public sentiment toward Russian President Vladimir Putin’s hard-line stance against the Ukrainian government.

Western news media, by contrast, have focused on U.S. and Ukrainian intelligence conclusions that the antiaircraft missile was fired from rebel-held territory.

Kozyrev said he expected that many of his colleagues would resort to a Soviet-era habit of making their points elliptically to avoid outright confrontation with authorities.

“There is a tradition in Russian literature of fables, and of speaking figuratively and hinting,” he said. “They won’t say what they really mean, but people will guess.”

Even before the law goes into effect, the space for online expression has been shrinking in recent months. Further restrictions that will require the data of Russian users to be stored on Russian soil — thus subjecting them to Russian legal oversight and monitoring — are set to become active next year.

A law that gives Russian authorities the power to block Web sites without any official explanation went into effect Feb. 1, and it was put to use a month later, blocking four Russian opposition Web sites, including the blog of anti-corruption politician Alexei Navalny, Russia’s most prominent anti-Kremlin leader. Navalny remains under house arrest on unrelated corruption charges and is barred from communicating with the media.

In the same month, another prominent independent news Web site, Lenta.ru, was transformed after the editor was fired and most of her staff left. That site’s coverage is now significantly more pro-Kremlin.

The new rules require anyone who has a daily online audience of more than 3,000 people to register with the Russian Internet-
oversight agency, Roskomnadzor, and to comply with mass media regulations that require bloggers to publish their names and contact details. The rules also hold them liable for any misinformation that they publish — along with any misinformation contained in comments posted on their Web sites, even if the bloggers did not write the comments.

Users also are forbidden from using the colorful Russian obscenities that are ubiquitous online, in popular culture and, for that matter, on the floor of Russia’s legislature. Fines on individuals range from $280 to $1,400. For organizations — such as Navalny’s anti-
corruption group — the fines can be up to $14,000 per violation.

Adding to the confusion — and to suspicions that the law would be used only as a bludgeon against the Kremlin’s political opponents — Roskomnadzor said this week that bloggers will need to register only if the agency asks them to do so.

“If you publish pictures of cats on your blog and if you do not use obscene language or disclose state secrets, this responsibility might not arise at all even if you have a million unique visits a day,” Roskomnadzor deputy director Maxim Ksenzov said in an interview with Lenta.ru on Tuesday.

A Roskomnadzor spokesman said that his agency was devoting about 35 people to the monitoring and registering effort and that it hoped to automate at least some portions of the process by the end of the year.

The haphazard and seemingly personalized nature of the registration efforts may mean that Russia is not yet approaching a more total technical control of the Internet, as is the case in China, analysts said. There, a countrywide firewall significantly curbs the content available to ordinary citizens, although it is possible to bypass it with a little technological trickery.

Anton Nossik, a prominent early Russian Internet figure, was skeptical that the new law would truly transform the landscape of repression — but only because authorities already have significant power to censor voices online. “Whenever they come for you, they have a rich choice of laws to come after you with,” he said.

And even pro-Kremlin lawmakers have said the regulations may be unwieldy.

“I don’t know how it’s supposed to work,” said Robert Shlegel, who, at 29, is the youngest member of Russia’s lower house of parliament and a member of the ruling United Russia party. He said that he thought that speech on the Internet should be regulated just like any other speech but that he did not see how the current legislation could be put into effect. “I’m trying to understand it myself,” he said.

The gradual diminution of diverse viewpoints is quickly having a chilling effect on Russian political discourse, said Vladimir Korsunsky, the editor of Grani.ru, one of the now-blocked Web sites. ­Grani.ru has lost half its audience.

When everyone has a single opinion, he said, “you have to be courageous to say, ‘No, I don’t agree with this.’ ”