STOCKHOLM — A Swedish court convicted a 61-year-old man on Monday of taking part in the 1994 genocide in Rwanda and sentenced him to life in prison. The case was noteworthy for being part of a transnational effort to hold people accountable for crimes against humanity, no matter where those crimes occurred.

The Stockholm District Court found that the man, Claver Berinkindi, a Rwandan who obtained Swedish citizenship in 2012, had participated in five massacres between April 18 and May 31, 1994. In the hills of Nyamure, in Rwanda’s Southern Province, he rallied people to participate in the killing of thousands of civilians, the court found. He was also involved in the deaths of hundreds of people who had sought refuge in a municipal building in the central Rwandan town of Muyira and in an adjacent adult education center. Trapped in the compound, hundreds of people were massacred.

“There were thousands of victims on the mountain, and hundreds of victims in the communal building,” Tora Holst, the chief prosecutor who leads a unit at the International Public Prosecution Office created in 2008 to focus on war crimes, said in a phone interview. “In the mountain, he collected and assembled people to go there, and he participated in the attack.”

The court found that Mr. Berinkindi had directly taken part in killings, using machetes, spears and clubs, Ms. Holst said. “It’s about the most serious crime known to mankind,” she said.