BEIRUT -- Hundreds of thousands of Syrians mounted the largest protests Friday since the uprising began more than four months ago, pouring into areas where the government crackdown has been most intense in a sign that security forces cannot break the revolt.
Syrian authorities fired on the crowds, killing at least 17 people and wounding more than 100, activists said.
In a significant show of the uprising's strength, thousands turned out in the capital, Damascus, which had seen only scattered protests. Until now, much of the dissent against President Bashar Assad has been in impoverished, remote areas.
"This is the heart of the regime," said David Schenker, director of the Program on Arab Politics at The Washington Institute for Near East Policy. "So I think if these protests (in Damascus) continue and gain strength, it will be the beginning of the end of the regime."
Massive rallies also were reported in areas that have come under military siege since the uprising began in March, with tanks and snipers trying to crush dissent. But the protesters have returned to the streets unbowed, defying the crackdown in a remarkable show of resilience.
Friday's protests stretched from Damascus and its suburbs to Hasakeh and Idlib provinces in the north, Daraa in the south and Latakia on the coast. Thousands converged on the flashpoint cities of Homs and Hama in central Syria, among other areas across the nation of 22 million.
Crowds chanted "We don't love you Bashar!" and "Leave Bashar!" before security forces and pro-regime gunmen opened fire with bullets and tear gas. Young men threw stones at security forces and shouted for the regime's downfall as they ran for cover.
"All hell broke loose, the firing was intense," an activist in Daraa, where the uprising began in March, told The Associated Press. He asked that his name not be used, fearing reprisals.
Activists say the crackdown has killed some 1,600 people, most of them unarmed protesters.
The government disputes the toll and blames a foreign conspiracy for the unrest, saying religious extremists -- not true reform-seekers -- are behind it.
Assad has acknowledged the need for reforms, but the opposition has been unwilling to negotiate while security forces fire on protesters.
Assad, 45, inherited power in 2000, and many believed the lanky, soft-spoken young leader might transform his late father's stagnant and brutal dictatorship into a modern state.
Over the past 11 years, however, hopes dimmed that Assad was a reformist at heart. As his regime escalates a brutal crackdown, it seems unlikely that he will regain political legitimacy.
"We have said that Syria can't go back to the way it was before, that Assad has lost his legitimacy in the eyes of his people because of the brutality of their crackdown, including today," U.S. Secretary of State Hillary Clinton told reporters in Istanbul, Turkey.
One of the largest protests Friday took place in Hama, Syria's fourth-largest city and an opposition stronghold that has a history of dissent.
Assad's late father and predecessor, Hafez, crushed a Sunni uprising in 1982 by shelling the town in a massacre that has been seared into the minds of Syrians, contributing to the pervasive sense of fear that silenced nearly every rumbling of dissent for decades.
Amnesty International has claimed that Hafez Assad's siege on Hama killed 10,000-25,000 people, although conflicting figures exist and the Syrian government has made no official estimate.
An activist in Hama said many people from nearby villages joined the protests there Friday.
Friday's death toll included 11 people in Damascus, three in the northwestern city of Idlib, one in the central city of Homs and two in Daraa in the south, according to the Local Coordinating Committees, which have a network of sources on the ground.
Syria has banned most foreign media and placed tight restrictions on reporters, making it difficult to independently confirm accounts.
Although Assad's regime is shaken, he still draws from a significant well of support among the business community, the middle classes and religious minorities.
But the opposition is determined to build on the uprising's strength.
Some opposition figures were expected to meet Saturday in neighboring Turkey to discuss alternatives to Assad, and another 45 dissidents planned a conference in Damascus on Saturday to form a "shadow government" to prepare for Assad's ouster.
Syria without Bashar Assad would be difficult to predict, in part because of the regime's web of allegiances to powerful forces including Hezbollah and Shiite powerhouse Iran.
Serious and prolonged unrest would hurt Hezbollah, the regime's proxy in Lebanon, and weaken Iran's influence in the Arab world.
But the country's mosaic of religions and sects is also potentially explosive.
The Assad regime is dominated by the Alawite minority, an offshoot of Shiite Islam, but the country is overwhelmingly Sunni Muslim.
Alawite dominance has bred resentments, which Assad has worked to tamp down by pushing a strictly secular identity in Syria. But the president now appears to be relying heavily on his Alawite power base, beginning with highly placed Assad relatives, to crush the resistance.
State-run Syrian TV blamed gunmen for Friday's unrest, saying they opened fire at demonstrators and security forces, killing a civilian in Idlib, another in the Damascus neighborhood of Qaboun and a police officers in Homs. The TV added that eight policemen were wounded in Homs as well.
In the past, the regime pointed to the quiet streets of Damascus to argue that the protest movement is marginal and cannot threaten Assad's power. But Friday's protests will make it more difficult to dismiss the uprising.
"Of course the regime will view this as very dangerous," Schenker said. "They will react in the most ferocious manner."