Moscow, Russia - Russia has put Reporters Without Borders (RSF) on its list of "undesirable" organisations, effectively banning the media watchdog from operating in the country, Moscow's justice ministry register showed Thursday.

Under a controversial law passed in 2015, but rarely used before its offensive on Ukraine, Russia can ban overseas organizations deemed a threat to national security.

Being branded as "undesirable" criminalizes the group and puts its staff at risk of prosecution.

The Kremlin has escalated its decade-long clampdown on independent media after sending troops to Ukraine in 2022, imposing sweeping censorship laws that effectively ban criticism of the army.

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RSF, based in France, regularly denounces attacks on freedom of expression and helps persecuted journalists.

Only last month, a Russian court jailed a journalist and former volunteer for the late opposition leader Alexey Navalny – whose organizations have been declared "extremist" in Russia – for 12 years.

Reporters Without Borders described her imprisonment as a "symbol of the Kremlin's repression of independent voices" and called for her release, as for all journalists in Russian detention.

The list of "undesirable" entities maintained by the justice ministry targets around 250 organizations now, including Amnesty International, Greenpeace, and Yale University.

It also features groups controlled by people long reviled by Russian authorities, including Hungarian-born billionaire George Soros and Mikhail Khodorkovsky, a Russian tycoon who opposed President Vladimir Putin.