The new tactics underline the evolution of the nine-week uprising, which has shown growing signs of resilience as it has weathered a ferocious crackdown. Since the uprising erupted with protests in a poor town in southern Syria, activists have tried to bring more organization and coordination to demonstrations that once seemed spontaneous.
Human rights activists estimate the death toll since the uprising started in mid-March at 1,000, and they say that at least 10,000 protesters are in jail. In addition to using live ammunition, security forces have beaten demonstrators with batons and dispersed them with water cannons, all tactics that organizers contend are more difficult to carry out after nightfall.
“The evening demonstrations are not the last thing,” said one activist in the northern city of Aleppo, who provided only his first name, Hudaifah. “We have other tactics for the coming weeks and months. We expect our uprising to continue for a long time.”
The revolt has posed a serious challenge to the authoritarian government of Mr. Assad, 44, an ophthalmologist who received his training in England and inherited his office in 2000 from his father, Hafez. Together, the Assad family has led this country, a strategic linchpin in the region, for four decades.
Activists say that demonstrations occur every evening in cities and towns across the country, including Damascus and its suburbs; Deir al Zour, to the northeast of the capital; Homs and Hama, in central Syria; and Aleppo and Idleb in the north.
Protesters are also gathering at night in the south, in villages near Dara’a, the impoverished town that became a flash point of the uprising when teenagers were arrested after being caught scrawling antigovernment graffiti on walls there.
The protests attract far fewer participants than those held after Friday Prayer. Some put the number just in the few hundreds. But protesters contend that they keep the pressure on the government and exhaust its security forces, which then spend the night patrolling neighborhoods and streets where demonstrations were held.
Organizers said evening protests were popular because they could attract people after they had left work and school. They also argue that it is easier for them to run away and hide from security forces in houses, shops, or dark, narrow alleys, and that the smaller numbers, dispersing quickly, help avoid widespread casualties and arrests.
The strategy is called “tayyara,” which translates as “flying.”
“We come up with ideas that security forces don’t expect,” Hudaifah, 28, said. “The Tunisian and Egyptian uprisings sparked our movement, but we are improving the tactics day by day.”
Hudaifah, like many others interviewed for this article, would not give his full name for fear of reprisal. He said he worked during the day for long hours as a tailor in his father’s shop and at night organized small demonstrations in his neighborhood.
Syrian officials have contended that they can end the uprising through force. But the longer the protests continue, the more untenable the government’s position becomes, both to its critics and its own constituents. That has put a premium on organizers to keep up the show of dissent, even on a small scale.
Organizers have begun filming the demonstrations with digital cameras, offering better quality images to the outside world than those of cellphone cameras. In small meetings, activists say, they have also tried to come up with other tactics, like seeking to deceive plainclothes security forces by pretending to be one of them or melting into the neighborhood.
“A few days ago I was in a protest when the security forces came,” said Tarek, 31, who works for a state-run construction company in Damascus. “I acted like an ordinary citizen and walked beside them, without panicking. They couldn’t recognize me. Some others are even behaving like security men.”
By all accounts, the uprising took Syrian officials by surprise. A few weeks before it started, Mr. Assad had declared in an interview that his country would not be affected by the uprisings that toppled leaders in Tunisia and Egypt.
As it has persisted, international criticism has mounted, and both the United States and European countries have imposed sanctions on Mr. Assad himself. The opposition abroad, meanwhile, plans to convene in Turkey next week in a bid to establish a more unified front.
“The protests will continue and will get bigger and stronger because the protesters are now more organized and more experienced,” said Bourhan Ghalioun, director of the Center for Contemporary Oriental Studies at the Sorbonne in Paris, who is also a prominent Syrian opposition figure.
“And they will keep protesting until they realize all their demands,” he said. “They will no longer accept a government imposed on them by the power of tanks.”