Russia is trying "to silence" the 2021 Nobel Peace Prize laureate Dmitry Muratov by branding the journalist a foreign agent, the body in charge of the prestigious award said Saturday.

"Dmitry Muratov was awarded the Nobel Peace Prize ... for his efforts to promote freedom of speech and freedom of information and independent journalism," Berit Reiss-Andersen, chair of the Norwegian Nobel Committee, said in a statement.

"It is sad that Russian authorities are now trying to silence him. The accusations against him are politically motivated," she added. Reiss-Andersen said the Norwegian Nobel Committee "continues to stand behind the important work" done by Muratov and the independent publication Novaya Gazeta.

Russia on Friday added Muratov, the editor of  Novaya Gazeta, to its list of foreign agents, a label authorities commonly use to stifle critics. Muratov "used foreign platforms to disseminate opinions aimed at forming a negative attitude towards the foreign and domestic policy of the Russian Federation," the justice ministry said.

It also accused Muratov of creating and distributing content from other foreign agents. "What is there to comment on? For comments, contact the ministry of justice", said Novaya Gazeta's website.

It added the foreign agents' list now included 674 "worthy" people and organisations. The label adds heavy administrative constraints and requires sources of funding to be disclosed. It also compels foreign agents to mark all publications -- including social media posts -- with a tag.

In 2021, when Muratov received the Nobel Peace Prize together with Filipina journalist Maria Ressa, he dedicated the award to Novaya Gazeta's "fallen" journalists who "gave up their lives for their profession."

Since 2000, Novaya Gazeta has seen six of its journalists and contributors killed, including investigative reporter Anna Politkovskaya, who was shot dead in Moscow in 2006.