Russia’s Internet watchdog agency threatened to block BuzzFeed, the viral news and entertainment Web site said Saturday. It is the first time a U.S. news organization has been touched by a Russian campaign against independent and opposition media outlets.

In an e-mail that BuzzFeed posted Friday, the Russian agency said that a BuzzFeed article about insurgent attacks in Chechnya, posted Wednesday and updated Thursday, “contains appeals to mass riots, extremist activities or participation in mass (public) actions.” The agency said the BuzzFeed site would be blocked in Russia if the offending content was not removed within a day.

In a follow-up e-mail to BuzzFeed, the agency clarified that the warning stemmed from a Chechen separatist video that had been embedded in the article. In the video, people who claimed to be the insurgents took responsibility for the attacks. The video had been posted on YouTube but appeared to be connected to a Chechen separatist Web site that is banned in Russia. YouTube subsequently removed the video, saying it violated its terms of service. BuzzFeed then removed the broken link, according to the post from Miriam Elder, BuzzFeed’s foreign editor.

A spokesman for the Internet watchdog agency said Saturday that the request had been made because “there were appeals to kill people” in the video. The follow-up e-mail from the agency to Buzzfeed thanks the Web site for its “cooperation,” suggesting that the site would not be shut down.

The threat against BuzzFeed, which has an expanding international news staff, came as Russia stepped up efforts to block Web sites it says are disseminating extremist content.

Buzzfeed employees work at the company's headquarters in New York. Russia’s threat against the news and entertainment Web site came as it stepped up efforts to block sources it says are disseminating extremist content. (Â© Brendan McDermid / Reuters)

This past week, the agency briefly banned the video-sharing site Vimeo because it was hosting an Islamic State recruiting film that had been posted in September. It also briefly banned the GitHub collaborative programming platform because users had posted content about suicide methods. The agency has also required Twitter to block specific user accounts in Russia.

Critics have said that the criteria are vague and that enforcement efforts are frequently used as cover for targeting opposition bloggers. In March, the agency blocked access to several opposition news Web sites.

There have not previously been publicized incidents in which the agency targeted Western English-language news sites. In August, it issued a warning to BBC Russia’s Russian-language site over an interview with an artist who advocated that Siberia have more autonomy within Russia.

China, which exercises greater control over the Internet than Russia does, has blocked several news sites within its borders, including the New York Times and Bloomberg News, over coverage critical of the Beijing government.