The Russian government has been clamping down on sites including Facebook, Twitter and YouTube in recent months for hosting content supporting jailed opposition figure Alexei Navalny.
Roskomnadzor, Russia's media watchdog, said the disruption of Twitter was intended to "protect Russian citizens" after the platform failed to comply with thousands of requests to delete content related to child pornography, drug use and calls for minors to commit suicide.
The watchdog did not reference calls to join opposition protests that had angered officials earlier this year.
Roskomandzor said the disruption would amount to a "slowdown in service speed" for all mobile users and 50 percent of desktop users, later adding that it would only affect photo and video content.
Officials accused foreign internet companies of interfering in Russia's domestic affairs in January over their failure to take down calls to participate in rallies in support of Navalny.
President Vladimir Putin then warned against the increasing influence of large tech companies, saying they were "competing" with sovereign states.
The watchdog warned that if Twitter ignored Russian law it could face further restrictions, including a complete ban.
Kremlin spokesman Dmitry Peskov insisted Russia had "no desire to block anything" and said the measures forcing companies to comply with Russian laws were "quite reasonable".
According to tech monitoring website Downdetector there was a spike in disruptions reported by Russian Twitter users on Wednesday morning.
Twitter did not immediately respond to AFP's request for comment.
Lawmakers on Wednesday welcomed the regulator's decision, warning that other social networks may be next.
For an optimal experience, please
