Russia on Monday placed a senior journalist with the Bellingcat investigative website on a wanted list, following his extensive reporting on Moscow's offensive in Ukraine.

Bulgarian journalist Christo Grozev's name was added to a list of wanted people on Russia's interior ministry website.

The ministry did not specify what crime he was wanted for.

But the RIA Novosti news agency quoted a source as saying that a criminal case had been opened against Grozev for "spreading fakes about the Russian army" -- legislation adopted after Moscow sent troops to Ukraine in February.

Russia's FSB domestic security agency had accused Grozev of helping Ukrainian intelligence.

Grozev is Bellingcat's chief Russia investigator, and has led investigations into the poisoning of opposition politician Alexei Navalny.

This year he has focused on Russia's military actions in Ukraine.

Moscow branded Bellingcat as an "undesirable" organisation in July, saying it posed a security threat to the country.

Bellingcat had already been branded a "foreign agent" in Russia last year.

Since Moscow sent troops to Ukraine in February, Bellingcat has largely focused on using open source material and social media to document alleged Russian war crimes.