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,” said an activist in Daraa, where the uprising began in March. 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.