Russian court decisions to ban the country's most prominent rights group, Memorial, have been criticised by the United Nations as moves that further weaken Russia's "dwindling human rights community".

The UN Human Rights Office said the legitimate voices of civil society should not be stigmatised, after a Moscow court hit Memorial with a second dissolution order in as many days.

Judge Mikhail Kazakov ordered the dissolution of Memorial's Human Rights Centre, which campaigns against contemporary rights abuses in Russia, at the request of prosecutors.

They accused the centre of failing to use on its publications the "foreign agent" label, which denotes organisations that receive funds from overseas.

On Tuesday, the country's Supreme Court ordered the dissolution of Memorial International, the group's central structure which chronicles Stalin-era purges and maintains the group's extensive archives in Moscow.

That ruling was slammed by US Secretary of State Antony Blinken and EU foreign policy chief Josep Borell, at a time when tensions are already high between Russia and NATO over the Ukraine conflict.

The trials cap a year that began with the jailing of President Vladimir Putin's top critic Alexei Navalny and signal the end of an era in Russia's post-Soviet democratisation process, which began 30 years ago this month.

On Wednesday, a UN spokesperson told AFP that it "deeply regrets" the Russian decisions. 

"These actions dissolve two of Russia's most respected human rights groups and further weaken the country's dwindling human rights community."

Memorial supporters protest following news of the organisation being shut down. Photo: AFP

"A free, diverse and active civil society is crucial for any society, and the legitimate voices of civil society should not be stigmatised, including through use of the term 'foreign agent'," said the spokeswoman for the Office of the UN High Commissioner for Human Rights, Michelle Bachelet.

"We urge the Russian authorities to protect and support people and organisations that work to advance human rights across the Russian Federation."

After the ruling, several dozen supporters applauded Memorial's lawyers outside of the courthouse in freezing temperatures.

"We had no illusions," said lawyer Ilya Novikov.

"But it is very important that this ship is sinking with a raised flag."

Alexander Cherkasov, head of Memorial's rights centre, branded the court decision "political" and said the group will continue working "somehow".

Supporter Yelena Ponomaryova described the ruling as the "collapse of the entire judicial system".

"It's a shameful decision," she said.

'Heartless closure'

Memorial, Russia's most prominent rights organisation, was founded in 1989 by Soviet dissidents including Nobel Peace Prize laureate Andrei Sakharov.

Memorial's rights centre has campaigned for the rights of political prisoners, migrants and other disadvantaged groups, and highlighted abuses, especially in the turbulent North Caucasus region that includes Chechnya. 

The centre has also compiled a list of political prisoners that includes Navalny and members of regional minorities outlawed in Russia including the Jehovah's Witnesses.

Memorial International said on Tuesday it will appeal the rulings and find "legal ways" to continue its work. 

"Memorial is not an organisation, it is not even a social movement," Memorial International said in a statement.

"Memorial is the need of the citizens of Russia to know the truth about its tragic past, about the fate of many millions of people."

On Tuesday, prosecutors charged that Memorial International "creates a false image of the USSR as a terrorist state and denigrates the memory of World War II".

Marie Struthers, Eastern Europe and Central Asia director at Amnesty International, said the accusations against Memorial were "bogus".

"The Russian authorities' heartless closure of the Memorial Human Rights Centre, an organisation that has provided assistance to thousands of people both at home and abroad for 30 years, is another blow to civil society in Russia," she said. 

This week's rulings against Memorial have come as no surprise to the group after Putin himself accused it of advocating for "terrorist and extremist organisations".

Memorial lawyer Ilya Novikov speaks to the media after the court ruling. Photo: AFP

Political observers say that the charges of extremism and terrorism have been used by Russian authorities to punish Putin critics.

The court ruling against Memorial International had sparked an international backlash.

"The people of Russia –- and the memory of the millions who suffered from Soviet-era repression –- deserve better," said Blinken.

Borrell tweeted: "Critical looks on their past are essential for the healthy development and progress of societies."

"Even by the standards of 2021, the closure of Memorial is an extraordinary event. A monstrous one," Meduza, an independent news website, said in an editorial.