MOSCOW — A Russian court on Monday sentenced a Muslim human rights activist to four years in a penal colony on drug possession charges widely seen as manufactured to further a crackdown on dissent in the Chechnya region.

The activist, Oyub Titiev, 61, had worked for years investigating allegations of abuse ranging from torture to murder under the increasingly autocratic rule of the Chechen leader, Ramzan Kadyrov.

Mr. Kadyrov publicly called Mr. Titiev a junkie after his arrest in January 2018.

“Drug addicts were arrested in Chechnya by the thousands, and no one came to their defense,” Mr. Kadyrov said on Chechen television at the time. But as soon as Mr. Titiev was arrested, he complained, “the entire world rose up.”

The organization where Mr. Titiev worked, a local branch of the Memorial Human Rights Center, was placed on a Russian government registry of “foreign agents” in 2014.