Iranians have looked for opportunities in recent months to display defiance against the rules of the clerical government. In Tuesday night’s annual fire festival, many found a chance.

Across Iran, thousands of men and women packed the streets as they danced wildly to music and jumped joyfully over large bonfires, according to videos on social media and interviews with Iranians. The police said the crowds were so large in Tehran and other cities that traffic came to a standstill for many hours and commuters had difficulty reaching public transportation, according to Iranian news reports.

Dancing, especially for men and women together, is banned in public in Iran and has long been a form of protest.

In many places, the gatherings turned political, with crowds chanting, “Freedom, freedom, freedom,” “Death to the dictator” and “Get lost, clerics,” according to videos and interviews with participants. In the city of Rasht in northern Iran, a crowd booed security officers who drove by in motorcycles, videos showed.

Iranians were celebrating the ancient Persian tradition of Chaharshanbeh Suri before the coming new year, Nowruz, which is on the first day of spring. In a ritual on the eve of the last Wednesday of the year, people jump over fire to cleanse the spirit from malaise of the old year and take on the glow of the flames in preparation for the new year.