A Russian opposition activist has released a report accusing Chechnya's Moscow-backed regional leader of involvement in the killing of a prominent Kremlin foe.

Ilya Yashin says Tuesday he had "no doubt" that Chechen leader Ramzan Kadyrov was behind the killing of Russian opposition leader Boris Nemtsov, who was shot dead on Feb.27, 2015, outside the Kremlin in Moscow.

Yashin said he was sure the suspected triggerman, an officer in Kadyrov's security force, and his accomplices wouldn't have acted without Kadyrov's approval. Kadyrov has denied the accusations and the official probe has failed to identify the mastermind.

Yashin's speech was interrupted by a bomb threat and police moved to clear the hall. An unidentified protester threw replica U.S. dollars at Yashin, suggesting perceived U.S. support for the Russian opposition.