“When a person leaves to become a terrorist, he can kill hundreds of innocents,” he said. “Those are the morals we are talking about. We should understand, the relatives must fight this first. If the relative, before the fact, reported it, he is not guilty. If he did not, he is guilty.”

By law, Russian security services have no authority to specifically target relatives. But the intelligence forces seldom let a detail like the lack of a legal basis interfere with their activities.

In Chechnya and neighboring Dagestan, they routinely burn or demolish the houses of people suspected of being insurgents or terrorists. Most strikingly, whole extended families are rounded up in high-profile cases, and are often held until the militant either gives up or is killed.

Maryam Akmedova, from Kabardino-Balkaria region in the North Caucasus, has seen it firsthand. Distressing though it was, she says she understood when Russian prosecutors accused her eldest son of participating in a terrorist attack, as he had never denied his involvement.

But her woes hardly stopped there.

Soon enough, security agents were questioning her younger son, though there was no evidence linking him to the attack his brother was accused of in the city of Nalchik in 2005. Eventually, the younger brother was shot and killed in 2013 by Russian security forces during an attempted arrest under murky circumstances.

“He had no involvement with anything,” Ms. Akmedova said in a telephone interview. “They killed him because his brother was in prison.”

The most sweeping application of the tactic came during the pacification of Chechnya, after Mr. Putin engineered the recapture of the separatist territory early in his tenure.