DAMASCUS, Syria – Troops opened fire on protesters in cities across Syria and pro- and anti-government crowds clashed in the capital’s historic old city as one of the Mideast’s most repressive regimes sought to put down demonstrations that exploded nationwide Friday demanding reform.

The upheaval sweeping the region definitively took root in Syria, as an eight-day uprising centered on a rural southern town dramatically expanded into protests by tens of thousands in multiple cities. The once-unimaginable scenario posed the biggest challenge in decades to Syria’s iron-fisted rule.

Protesters wept over the bloodied bodies of slain comrades and massive crowds chanted anti-government slogans, then fled as gunfire erupted, according to footage posted online. Security forces shot to death more than 15 people in at least six cities and villages, including a suburb of the capital, Damascus, witnesses said.

The regime of President Bashar Assad, an ally of Iran and supporter of militant groups around the region, had seemed immune from the Middle East’s three-month wave of popular uprising. His security forces, which have long silenced the slightest signs of dissent, quickly snuffed out smaller attempts at protests last month.

Syrians also have fearful memories of the brutal crackdown unleashed by his father, Hafez Assad, when Muslim fundamentalists in the central town of Hama tried an uprising in 1982: Thousands were killed and parts of the city were flattened by artillery and bulldozers.

The Assads’ leadership — centered on members of their Alawi minority sect, a branch of Shiite Islam in this mainly Sunni nation — have built their rule by mixing draconian repression with increasing economic freedom, maintaining the loyalty of the wealthy Sunni merchant class in the prosperous cities of Damascus and Aleppo.

Bashar Assad now faces the same dilemma confronted by the leaders of Tunisia, Egypt, Yemen and Bahrain — ratchet up violence or offer concessions. A day earlier, his government seemed to test the latter track, offering to consider lifting draconian emergency laws and promising increased pay and benefits for state workers.

As massive crowds rejected the offers, the worst violence appeared centered around Daraa, where the arrest of a group of young men for spraying anti-regime graffiti last week set off a cycle of growing demonstrations and increasingly violent government crackdowns.

The Syrian government said 34 had been slain in Daraa before Friday, while the U.N. human rights office put the figure at 37. Activists said it was as high as 100.