Another post showed a mother with her daughter. "The beautiful seaside in Kish [Island]," the younger woman wrote. "We strolled on the rocks and experienced the cool breeze flowing through our hair. Is this a big request?"

A young woman from the city of Fuman, in the northern province of Gilan, sent a picture of her in the woods. "I took this picture stealthily in the spring," she wrote. "It makes me feel happy."

Alinejad said she had been bombarded with messages and pictures since launching Stealthy Freedoms of Iranian Women. "I've hardly slept in three days because of the number of pictures and messages I have received."

Alinejad said she did her best to verify that the pictures were sent from genuine accounts and asked people for permission before publishing them, but did not reveal their full names.

"I have no intention whatsoever to encourage people to defy the forced hijab or stand up against it,"she said. "I just want to give voice to thousands and thousands of Iranian women who think they have no platform to have their say."

Alinejad said she was not opposed to the hijab, which covers the head and chest, but she believed people should have the freedom to choose.

She said: "I want to live in a country where both me, who doesn't have hijab, and my sister, who prefers hijab, can live along[side] each other."

In the stifling heat of an Iranian summer, many women in the country push the boundaries, wearing loose hijab or sporting clothing and haircuts the authorities deem "un-Islamic".

The religious police are often deployed on the streets, cracking down on those with "bad hijab".