On Tehran's bustling streets, signs of change are unmistakable. Women walk unveiled in jeans and sneakers, men and women linger together in cafés where Western music hums softly, and couples stroll hand-in-hand — subtle acts that chip away at the rigid social codes that have long defined the Islamic Republic. But beneath the surface, a darker reality is unfolding. Iran's clerical rulers are intensifying a crackdown on political dissent to instill fear and prevent unrest, four activists inside Iran said.

Hundreds of journalists, lawyers, students, writers, and human rights advocates have been harassed, summoned, detained, or subjected to other punitive measures in recent months, according to rights groups and activists.

The authorities' strategy is calculated: relax visible restrictions to soothe public opinion amid Iran's growing economic isolation, while quietly intensifying a crackdown on political dissent, three Iranian officials and one former senior reformist official said.