Kurds make up about 10 percent of Syria’s 20 million people, concentrated in the remote northeast, which borders Iraq and Turkey, but also in Damascus and Aleppo, the country’s two largest cities. They have long faced harassment and discrimination, and for years many were denied Syrian citizenship. Though the community has sympathized with the uprising, its traditional leadership has yet to decisively enter the fray against Mr. Assad, and the government itself, veering between crackdown and concession, had appeared reluctant to provoke the Kurds.

Early in the uprising, the government informally negotiated with Kurdish leaders, reaching what some had termed “a gentleman’s agreement” to forestall mass unrest. Mr. Assad even promised to give tens of thousands citizenship in April, though activists say few have received it.

The Syrian news agency blamed an “armed terrorist group” for Mr. Tammo’s death, a phrase it often deploys to underline its view of the uprising as an armed insurgency led by militant Islamists.

“There’s a real potential for it getting out of hand,” said Peter Harling, a Syria-based analyst and researcher with the International Crisis Group.

He said the killing was a vivid illustration of the consequences of the government’s shift toward what it calls the “security solution,” a decision that seems to have been made before the Muslim holy month of Ramadan began in August.

“The security solution essentially amounts to giving a free hand to the security services to dramatically raise the levels of violence in an attempt to restore the wall of fear,” Mr. Harling said. “In doing so, the regime has undermined its own ability to think and act politically. This is sheer violence, with no limits, a ‘solution’ that has every chance of creating many new problems.”

Activists said Mr. Tammo’s funeral quickly turned into a rally attended by as many as 50,000 people. Video broadcast on Al Jazeera showed his coffin draped in a Kurdish flag and covered in flowers. At the funeral, activists said, mourners shouted for the fall of Mr. Assad, who inherited power 11 years ago from his father, Hafez.