A Franco-Russian opponent of President Vladimir Putin has applied for political asylum in Bulgaria, where he is fighting extradition to Russia, his lawyer said Wednesday.

Nikolay Koblyakov, co-founder of an anti-Putin non-governmental organisation active in France, is wanted by Russia on fraud charges and was arrested on an Interpol warrant on July 29.

Koblyakov denies any wrongdoing, calling the accusations politically motivated.

He "filed on Monday a request for political asylum motivated by the threat for political persecution by the Russian authorities," his lawyer Biliana Kotsakova told AFP.

Activists say that even before the Ukraine crisis sent Moscow's relations with the West into a tailspin earlier this year, Putin had been making life hard for NGOs in order to silence dissent.

In 2012 a law was passed in Russia obliging all organisations that receive money from abroad and engage in politically related activity to register as "foreign agents".

Koblyakov, who has dual Russian and French nationality, was initially detained at Sofia airport in former communist EU member Bulgaria. On Monday, when Russia officially demanded his extradition, he was placed under house arrest.

His NGO Russie-Liberte ("Russia-Liberty") called in a statement on Bulgaria to grant Koblyakov asylum, saying his treatment in Russia would "not conform with the European Convention on Human Rights".