PARAMARIBO, Suriname — A court in the tiny South American country of Suriname convicted President Desi Bouterse on Friday in the 1982 killings of 15 political opponents and sentenced him to 20 years in prison.

The decision by a panel of three judges marked the end of a historic trial that began in November 2007, although it was not immediately clear what would happen next. Shortly after the court issued its verdict, the government asked Suriname’s more than half a million inhabitants to remain calm.

“Democracy remains of paramount importance,” officials said in a statement.

Mr. Bouterse, 74, was on an official trip in China and could not be immediately reached for comment.

He accepted “political responsibility” for the killings in 2007 when he offered his first public apology but insisted he was not present.