“Syria is one of the last secular regimes in the Arab world, and they are targeting Syria,” said Buthaina Shaaban, a presidential political and media adviser, warning that the West would rue the day that it enabled Islamist regimes. She rejected the idea that any true Syrian could rise against the government, saying, “Colonialism has always found agents inside the country.”

But that view does not seem to explain events unfolding on the streets.

The seemingly routine flow of life in central Damascus could leave the impression that there is no crisis, or that the security approach is effective. Yet beneath the mundane, unease grips the capital as fear of civil war supplants hopes for a peaceful transition to democracy. Damascus residents describe the restive suburbs as severed from the city by government checkpoints, and while the security forces control those areas by day, the night belongs to the rebels. A request to visit the suburbs was denied “for your own safety” by a Syrian government official.

Protesters hold “flying demonstrations” inside the city, trying to subvert the security forces, with a few people gathering briefly to be filmed shouting antigovernment slogans. Damascenes say that they have become so accustomed to hearing slogans chanted in the background, given the almost daily pro-government rallies organized by the government, that it takes a few minutes to register that people are cursing Mr. Assad. By the time they seek the source, the protesters have faded away.

Yet security forces seem omnipresent, usually materializing in minutes. Government critics say myriad supporters have been recruited into the shabiha, or thugs, as the loyalist forces are known.

A recent flash demonstration near the central Cham Palace Hotel was dispersed by a group of waiters who flew out of a nearby cafe with truncheons, a witness said. Many university campuses remain tense because student members of the ruling Baath Party have been reporting antigovernment classmates to the secret police.

A young professional said that one of his workers filming a long line of people waiting for scarce cooking-gas bottles had been severely beaten by security agents who showed up within two minutes to arrest him. It is a common fate described for those seen filming, and the government has just banned iPhones.

“It was just a long queue, nothing political,” said the professional, speaking anonymously like many Syrians for fear of reprisals. “They think that if they hide everything it will go away, but it won’t.”