CAIRO — Tens of thousands of Egyptian Islamists poured into Tahrir Square on Friday calling for a state bound by strict religious law and delivering a persuasive show of force in a turbulent country showing deep divisions and growing signs of polarization.

The shape of Egypt five months into its revolution remains distinctly undecided, and Islamists have long been the best organized political force in this religiously conservative country. Some activists speculated that their show of strength would serve as a jolt to the secular forces who helped to start the revolution but who remain divided, largely ineffectual and woefully unprepared for coming elections.

Others speculated that it might force groups to pick sides in a country where the glow of unity after President Hosni Mubarak’s fall in February has dimmed amid recriminations over the pace, style and substance of change.

“Islamic, Islamic,” went a popular chant. “Neither secular nor liberal.”

After days of negotiations between the rival factions, the demonstration Friday had been billed as a show of national unity, but adherents to a spectrum of religious movements — from the most puritan and conservative, known as Salafists, to the comparatively more moderate Muslim Brotherhood — vastly outnumbered other voices in a sun-drenched Tahrir Square. The numbers of Salafists, in particular, represented the most definitive declaration yet that they represent a formidable force in Egyptian politics, riding an ascent since the revolution that has surprised and unnerved many secular and liberal activists — and poses new challenges to the Muslim Brotherhood.