Russia's state communications watchdog, Roskomnadzor, has threatened to block Twitter in a month's time if the social-media network doesn't begin removing banned content.
Roskomnadzor last week announced a slowing down, or throttling, of Twitter's speed across the country for its "failure" to remove what it said was banned content that encouraged suicide among children and information about drugs and child pornography.
On March 16, Roskomnadzor's deputy head, Vadim Subbotin, said the company still wasn't complying with the demands of the Russian authorities.
"Twitter doesn't react to our requests appropriately, and if things go on like this, then in a month it will be blocked, on an out-of-court basis," Subbotin was quoted by the Interfax news agency as saying.
Roskomnadzor said on March 10 that the measure was meant "to protect Russian citizens from the influence of illegal content" and threatened to fully block the U.S. social network if it did not act.
The action came amid Russian efforts to tighten control on social media and a clampdown on platforms that have been used to organize protests in support of jailed opposition leader Aleksei Navalny.
Last month, a law came into force that states social networks must themselves find and delete content banned by Russian law. If a social network is unable to determine if content contains banned materials, it must send the content to Roskomnadzor for an evaluation.
The agency had said that, as of March 10, Twitter had 3,168 posts with banned content on its site, including more than 2,500 posts encouraging suicide among minors. It also referred to content on illegal drugs and pornography.
Subbotin said that the Russian regulator at this point "is not registering specific steps by Twitter to remove prohibited content."
Aleksei Pushkov, chairman of the Information Policy Committee of the Federation Council, Russia's upper chamber of parliament, said on March 16 that the authorities should consider completely blocking Twitter, but on a temporary basis.
"My personal position as the head of the Committee on Informational policy is that we can block Twitter completely, but for a limited period -- for a month," Pushkov was quoted as saying by TASS.
"By doing so we give them a warning signal that this is not just idle talk," Pushkov said.
Twitter did not respond immediately to an e-mail request for comment.
Roskomnadzor's Subbotin has warned that "it is possible" similar measures could be imposed against other social networks such as Facebook in the future if they do not follow Russian regulations.
Moscow has been trying to curb social media in recent years amid increasing protests among citizens, especially younger Russians, and social media's role in amplifying dissent.
Officials in January accused foreign Internet companies of interfering in Russia's domestic affairs over their failure to take down calls to participate in rallies in support of Navalny.
The government has previously moved to tighten control of social media by requiring online services to store the personal data of Russian users on servers in Russia. Facebook and Twitter have been fined for failing to comply with the law.
Russian Foreign Ministry spokeswoman Maria Zakharova late last year accused Facebook and Twitter of "open censorship" after they blocked Russian accounts and content and after Twitter labeled government and state-affiliated media accounts.
Late last month Roskomnadzor demanded Twitter explain why it removed 100 accounts linked to Russia.
Twitter said in response that the accounts "amplified narratives that were aligned with the Russian government, focused on undermining faith in the NATO alliance and its stability," and targeted the United States and the European Union.
In 2014, authorities adopted a law requiring online services to store the personal data of Russian users on servers in Russia and have since tried to make Facebook and Twitter comply with it.
Both social-media giants have been repeatedly fined, first small amounts of around $50 and last year the equivalent of $63,000 each, for not complying.
