Putin claims hand grenade caused crash that killed Wagner chief Prigozhin

Fragments of hand grenades were found in bodies of plane crash victims, according to Putin.
Crash occurred in August, killing Prigozhin and 9 others associated with Wagner Group.
Prigozhin led failed rebellion against Russian military 2 months before crash.
US intelligence suggests intentional explosion brought plane down.
Kremlin denies involvement despite suspicions Putin ordered assassination.