The court ruled that the group Memorial must be closed for breaking the law on foreign agents.

The group says the lawsuit was politically motivated and has announced it will appeal the ruling before the European Court of Human Rights.

Memorial's lawyer Henry Reznik told Sky News that the court's ruling was "a politically motivated decision and unfortunately we are not surprised with it".

What is Memorial?

The international human rights group rose to prominence for its studies of political repression in the Soviet Union and currently encompasses more than 50 smaller groups in Russia and abroad.

It was founded by dissidents before the fall of the Iron Curtain and initially focused on documenting the crimes of the Stalinist era, but has more recently spoken out against the repression of critics of President Vladimir Putin's regime.

It has been on an official list of "foreign agents" since 2015.

Last month, Memorial International and its subsidiary Memorial Human Rights Centre were accused by prosecutors of violating the foreign agent law, with the supreme court asked to shut them down.

Prosecutors claimed that Memorial International breached the foreign agent regulations by not marking all its publications, including social media posts, with a "foreign agent" label, as required by the law.

They also accused the Memorial Human Rights Centre of condoning terrorism and extremism.

What is Russia's foreign agents law?

The law mandates a non-governmental organisation, a media outlet, an informal movement or an individual to be listed as a foreign agent for having received foreign funding - even a small donation from a foreign national counts - and engaging in loosely defined political activity.

The label comes with excessive government scrutiny and connotations that can negatively affect those who are tagged as such.

Former British ambassador to Moscow Sir Andrew Wood told Sky News: "It's an arbitrary law in which people are accused of being foreign agents and therefore, somehow connected with foreign intelligence and so on, but you don't require proof to nominate someone for that.

"You do require a court hearing to abolish an organisation as such, and they've had that but it was obviously heavily biased."

The Tass news agency reported that a state prosecutor told the hearing Memorial had organised campaigns aimed at discrediting the Russian authorities.

Mr Putin said earlier this month that Memorial had defended groups that Russia considered extremist and terrorist, and among those it said were victims of political repression were Nazi collaborators.

The work carried out by Memorial includes examinations of repressions carried out by Soviet state security bodies, such as the KGB, where Mr Putin once served as a spy.

As the verdict of the court was announced, police escorted away several protesters outside.