Internet service providers in Russia began blocking access to opposition politician Aleksei Navalny's website on February 15 following an order from the country's communications regulator, Roskomnadzor, according to news reports and social-media posts by Navalny and others.
The development came as Roskomnadzor told Navalny -- along with YouTube and Instagram -- that they must delete or block access to a video and photos in an online report about an alleged meeting between billionaire Oleg Deripaska and Deputy Prime Minister Sergei Prikhodko, a longtime former senior adviser to President Vladimir Putin.
Navalny defied the order, which followed a court ruling that publication of the video and photos violated the privacy rights of Derispaska, who filed a lawsuit over the matter after Navalny posted the report on his website on February 8.
Navalny's report, which he says is part of a growing body of evidence of corruption in circles close to Putin, draws on photos and videos published earlier on the social-media account of a Belarusian woman who goes by the name Nastya Rybka and says she had an affair with Deripaska.
A February 14 deadline that Navalny said was set by Roskomnadzor passed without incident, but reports that navalny.com was inaccessible for many in Russia began flowing in on February 15.
"The first reports that navalny.com does not open have come in," Navalny tweeted, and other Internet users said on Twitter that they were unable to open the site through major Russian Internet providers.
"Roskomnadzor has begun blocking navalny.com at the behest of Deripaska. The site still opens through some providers, but that is temporary," Navalny, who has accused Roskomnadzor of "censorship," said in a subsequent tweet.
Later on February 15, however, senior Navalny associate Leonid Volkov tweeted that the site was widely accessible, calling Roskomnadzor "cretins" and saying that "the 'blocking' mechanism can be broken with little effort."
Meanwhile, the Interfax news agency reported that Roskomnadzor was pressing its demand that U.S. Internet giant Google delete or block access to the videos and photos on YouTube.
"Roskomnadzor expects a decision from...Google on the deletion from YouTube of the materials [referred to] in the court decision. Roskomnadzor hopes that Google's decision will be positive," Interfax quoted the regulator's press service as saying. It said that the material "has been deleted" from Instagram.
There was no immediate comment from Google.
WATCH: The Navalny video (with English subtitles)
Navalny's eye-catching report caused a potentially embarrassing splash ahead of a March 18 election in which Putin, who has been president or prime minister since 1999, appears certain to win a new six-year term but is said to be hoping for a convincing victory that would strengthen his mandate and further cement his power.
Navalny, a vocal foe of Putin who has organized large street protests on several occasions and published a series of reports alleging corruption in Russia's ruling elite, has been barred from the presidential race due to a conviction on financial-crimes charges he contends were fabricated by the Kremlin to sideline him.
In a video posted on Twitter, Navalny said that government moves to block his website had two goals: to "serve the oligarch Deripaska and the bureaucrat Prikhodko" while also undermining his efforts to mount a massive boycott of the presidential election and to organize an election observation campaign.
Supporters posted the address of a "mirror site" where the report on the alleged meeting between Deripaska and Prikhodko could be seen by Internet users in Russia, and Navalny tweeted in English: "You can still see our investigation on YouTube with English subtitles."
The February 8 report is based largely on the social-media account of Nastya Rybka, who has written a book about her work as an escort and said on television last year that she had been hired by a modeling agency to spend time at Deripaska's yacht.
Rybka, whose real name is Anastasia Vashukevich, posted videos and photos in 2016 that appear to show Deripaska on his yacht talking with Prikhodko -- as well as her cuddling with the tycoon.
AFP reported early on February 16 that Rybka's Instagram posts supporting Navalny's allegations were no longer accessible in Russia, although Navalny's 25-minute YouTube video was still accessible.
AFP said it learned that Rybka removed most of the photos from Instagram herself, while Instagram took down a few remaining posts to avoid being banned in Russia.
"When governments believe that something on the Internet violates their laws, they may contact companies and ask us to restrict access to that content," a spokesperson for Instagram, which is owned by Facebook, told AFP.
"We review such requests carefully in light of local laws and where appropriate, we make it unavailable in the relevant country or territory," the spokesperson said.
Navalny in his video also quoted public records, which he said indicated that Prikhodko spent several days on the yacht and was flown there by Deripaska's private jet.
Navalny's anticorruption foundation earlier published documents suggesting that Prikhodko, a longtime public servant with no significant private income, owns a luxurious mansion outside Moscow.
Deripaska has not denied meeting with Prikhodko on the yacht, but in a February 9 statement he said he had done nothing illegal and warned media outlets not to disseminate what he called "mendacious accusations."
He also obtained a court order demanding the removal of 14 Instagram posts and seven YouTube clips, and Roskomnadzor based its calls for the deletion of the materials on that order.