Umar S. Israilov saw the men who had come to kill him. They confronted him in the neighborhood where he lived in hiding in Vienna. He must have sensed their intentions, because he ran.

For more than two years, Mr. Israilov, a Chechen in exile, had formally accused Russia’s government of allowing a macabre pattern of crimes in Chechnya. Even by the dark norms of violence in the Caucasus, his accusations were extraordinary.

A rebel fighter turned bodyguard of Ramzan A. Kadyrov, Chechnya’s current president, Mr. Israilov had access to the inner ring of Chechen power. Mr. Kadyrov’s career has been sponsored by Prime Minister Vladimir V. Putin of Russia, who as president lifted him from obscurity with unwavering Kremlin support.

In written legal complaints, Mr. Israilov described many brutal acts by Mr. Kadyrov and his subordinates, including executions of illegally detained men. One executed man, Mr. Israilov said, had been beaten with a shovel handle by Mr. Kadyrov and Adam Delimkhanov, now a member of Russia’s Parliament. Another prisoner, the defector said, was sodomized by a prominent police officer and at Mr. Kadyrov’s order put to death.