Under President Paul Kagame, this country, which exploded in ethnic bloodshed 16 years ago, is now one of the safest, cleanest and least corrupt nations on the continent. The capital, Kigali, is not ringed by sprawling slums, and carjackings — a deadly problem in many African cities — are virtually unheard of here. The roads are smoothly paved; there is national health insurance; neighborhoods hold monthly cleanups; the computer network is among the best in the region; and the public fountains are full of water, not weeds. All of this has been accomplished in one of the world’s poorest countries.

But while the nation continues to be praised as a darling of the foreign aid world and something of a central African utopia, it is increasingly intolerant of political dissent, or sometimes even dialogue, and bubbling with bottled-up tensions. Recent grenade attacks in Kigali and a shake-up in the army showed that even one of the cornerstones of the new Rwandan state — personal security — might be in danger.

“Kagame’s strategy for stability is a dangerous, long-term gamble,” said Kenneth Roth, executive director of Human Rights Watch. “By stymieing a political opposition, an independent press or a critical civil society — in short, by not allowing democratic institutions to form — Kagame is leaving people little to identify with but their ethnic group.”

Image Hundreds have been sent to Iwawa Island without trial. Credit... Jehad Nga for The New York Times

With less than four months to go before national elections, few of the major opposition parties have been allowed to register. Some opposition supporters have been attacked inside government offices; others have been jailed. Several prominent government officials who recently broke ranks with Mr. Kagame defected to other African nations, saying they feared for their lives. The BBC local-language radio service was shut down for a time because the Rwandan government did not like the way it was talking about the genocide of 1994.