The report, released Tuesday, accused Kadyrov (pictured above) of posing a national security threat to Russia, and said there was "no doubt" he was behind the murder of Nemtsov, an opposition leader shot dead last February.
Yashin also said Kadyrov, Russian President Vladimir Putin's strongman in Chechnya, was carving out a separatist state right under Putin's nose.
"We are opposing a corrupt, dangerous regime that poses a threat to Russia and Chechnya," said Yashin, an opposition activist.
"Today's regime in Chechnya you can describe as a personal rule."
The 39-year-old Kadyrov, who rose to power in 2007 after serving as a rebel fighter, has amassed a fortune from federal subsidies given to Chechnya, according to the report. He has also been allowed under Putin to form his own personal army.
Yashin also said there was little doubt the gunman who killed Nemtsov had acted with Kadyrov's approval.
The Chechen leader took to Instagram following the release of the report, where he described Yashin's accusations as nothing but "chatter."
blc/es (AP, AFP)