Some observers are expressing concern that blocking Krym.Realii may be the first step towards banning RFE/RL in its entirety in Russia.

"This is an aggressive act that uses the outrageous pretext of extremism to censor RFE/RL and prevent audiences in Russia and Crimea from learning the truth about the annexation," RFE/RL Editor in Chief Nenad Pejic said in a statement on May 12.

"We condemn it as an attack on RFE/RL's operations and the public's fundamental right to freely access information," he added.

Read alsoRussia blocking Radio Liberty's Krym.Realii websiteCrimea's Moscow-appointed, de facto Prosecutor-General Natalia Poklonskaya posted a statement on May 12 saying that Russia's Internet regulator, Roskomnadzor, had launched measures to block and shut down the site. Her office had earlier issued a call for the website's closure on April 19, claiming it seeks to "discredit the Russian Federation, incites inter-ethnic hatred and promotes extremism." A contributor to the website was arrestedthat day, drawing a sharp rebuke from U.S. Embassy in Kyiv spokesman Jonathan Lalley, who called it an example "of the Russian government’s growing crackdown on independent voices in Russia and Russia-occupied Crimea."

Read alsoCrimean de facto Supreme Court bans Mejlis

According to Roskomnadzor's website, decisions to block access toKrym.Realii were adopted in September 2015 in connection with Russia's law on extremism; it is unclear why these decisions are being implemented now.

Krym.Realii is one of the last remaining sources for independent reporting about Russia-annexed Crimea. It is published in Russian, Ukrainian, and Crimean-Tatar languages, and has logged an average of 2.2 million visits monthly to its website over the past 12-month period.