The strongman leader of Russia's Chechnya republic says Russian opposition activists should be considered traitors and punished for their "subversive activities."

The statement by Ramzan Kadyrov drew harsh criticism on Wednesday from rights activists, including Russian human rights ombudsman Ella Pamfilova.

The opposition has come under increased pressure since the mass protests in Moscow that accompanied Vladimir Putin's return to the presidency in 2012.

Kadyrov told Chechen journalists that opposition activists were trying to use Russia's current economic difficulties to shake up the political situation and should be brought to judgment as "enemies of the people" and traitors.

His comments were seen as ominous because rights activists have accused Kadyrov of ordering the killings of some who oppose him or Putin. Kadyrov has denied the accusations.