The ambush came from the left, from a side street which led up the hill to Mokattam mosque. A rush of hundreds of men running down on the march of anti-government protesters, bringing a sudden clatter of rocks landing all around, the crack of shots fired and the whizz of tear gas canisters. Sticks, stones and metal bars flew through the smoke in both directions and screaming women and men ran back the way they came.

Dozens of manned police vans remained parked a kilometre away. The only sirens came from ambulances that drove through the crowds and past burning vehicles to take some 40 injured people to hospital.

One angry woman with a bleeding mouth and eyes streaming from the tear gas pulled off her headscarf and stood yelling at the other side, the supporters of the ruling Muslim Brotherhood: "You are not Islam! You are not Egypt! Where is my freedom?"

So go most Fridays in Cairo over the past few weeks as liberal Egyptians have shown their virulent opposition to the president, Mohamed Morsi, as he has awarded himself new powers and pushed through a deeply contentious new constitution. Several buildings of the Muslim Brotherhood, the group behind Morsi, have been burned. In post-Arab spring Egypt the revolution continues. But it's women of all classes who have found themselves most alienated – written out of the jostling for power and subjected to a skyrocketing number of sex assaults, rapes and harassment.

Women who stood shoulder to shoulder with men during the 2011 Tahrir Square protests that brought down Hosni Mubarak found their position in society undermined almost immediately. The parliamentary quota for women was removed without debate and a promised female vice-president failed to materialise, amid what political commentator Moushira Khattab called "a radical anti-feminist sentiment". Morsi threatened but stopped short of decriminalising Egypt's practice of female genital mutilation, carried out on almost three-quarters of Egyptian girls, making it clear he would not tackle an issue he called "a family matter".

The new constitution has swept away recognition of women's rights and left the door open to the legalisation of perhaps Egypt's most crippling social issue – underage marriage. Draft legislation that would allow the legal age of marriage to be lowered from 18 to 13 has been drawn up while clerics within the Muslim Brotherhood have indicated that marriage at the age of nine for girls is acceptable.

"They see women as, number one, objects of sex and, number two, to clean their floors. This is what the Egyptian 'brotherhood' is all about," said Fatma, 24, an engineering graduate marching with her friends, some in burqas, some in headscarves. The women keep close together, arms linked and eyes alert for the men flying down the side of the demonstration on motorcycles grabbing and screaming at females. "They want to marry us at nine years old. Are these really the kind of men we want to run our country? Paedophiles?"

Political progress has been slow, with parliamentary elections scheduled for April now postponed with no new date. Frustrations have built.

"They are like a pack of dogs, tearing out the weakest first, raping and harassing the women and the girls, getting rid of them, and then fighting among themselves to be pack leader," said Aya Kadry, 62.

Around Cairo hundreds of tower blocks are being built, extending the Arab world's largest city leg by leg into the desert. This is where the vast majority of Egypt's women are already living the constrained lives that the educated and middle-classes fear will be imposed by a radical government. Child marriage is common, the norm among the poor. Doctors are bribed to sign documents asserting a 14-year-old is 18 but most people don't have the money so marriages go ahead without registration. Underage girls then have children who, essentially illegal, cannot have their births registered. Without papers those children cannot attend school, encasing a whole new generation in poverty.

In the poor district of Ezbet Khairallah 10 women are sitting around a metal cash box, holding the weekly meeting of their savings and loans group. Set up by the charity Plan Egypt, it encourages women to squirrel away a few coins when they can and to discuss problems.

"We do not really have time to talk to our neighbours, there is a great burden of things to do in the home and for some of us our husbands do not like us to go out of doors, although we have convinced them we should meet for this social fund because it will help all the family," said Seham Ahmed, 38, who is taking the opportunity to show the group how to make a basic liquid soap.

"I was married at 14," she said, thumping a stick round a battered bucket and most of the women around her nod. "Pulled out of school one day and married that night. I hope my daughters can wait a little while but it's quite difficult for girls who are not married at an early age to find a good man later and there is a lot of pressure. And fathers want girls gone because it is one mouth less to feed."

Asmaa Mohamed Fawzy is 21. She was engaged but her family allowed her to break it off when her best friend died in childbirth aged 16. "I liked having the ring but I was only 15 and didn't know any better. When Aya died it was a miserable tragedy and I'm very lucky that my mum agreed with me I should not get married. I get teased and bullied. They shout I am not pretty enough, why am I the ugly one, but I do not want to die or to have children who cannot go to school. It is probably too late for me now and I'm sad I won't have children."

Her mother, Naghzaky Abdalla, 47, also endures being shunned by her neighbours. "When her friend died I too made up my mind. We only have one so we can afford to protect her. A neighbour had died at 15 of bleeding: the doctors wouldn't treat her because she was married illegally and they don't want to get involved. The girls' bodies are not ready for childbirth and they are not ready for sexual relations which makes their husbands impatient with them.

"Three girls in our street stay indoors now for ever because their husbands divorced them. If they cannot prove they were married and they are not virgins then they cannot get married again so they are shunned. Many are divorced because of course these girls are too young to understand what marriage means, she is still a child. In our community, though, a girl should be married before she is 16, maximum."

Mrs Gihan, 45, a community activist with strong views, is fervently for the lowering the age of marriage to 13 in law. "We must do this," she said. "Because all the unregistered children who cannot go to school need to be helped. These girls are denied healthcare, their children are denied a future. They have already decreased the legal age of work from 14 to 12 and I think this age too should be lowered. When Mubarak listened to international pressure and raised the age to 18 it changed nothing here. If you decree a legal age then you simply criminalise and marginalise. Men leave their wives before they turn 18 and their children are seen as being born into prostitution. We will raise awareness and stop child marriage this way."

The stench of human waste coming from the river in another poor Cairo district, Manial Sheiha, is overpowering. The streets of packed earth are quiet with only children to be seen.

Nawal Rashid opens her door but remains on one side of the deep concrete threshold that she cannot cross – or allow visitors to cross – without her 70-year-old husband's permission. He is at work. Her three-year-old son plays behind her and she insists she married at 18 – which makes her 21 now – but her neighbours all say she was 14. "I accepted the older man to help my family as there were four other children and my parents are very poor. I am quite content and happy to have sacrificed myself for my family."

Next door is Etab, 19. She has two children and has returned to stay with her despairing mother Nearnat, 42, her ageing father and her three siblings.

"We thought by marrying her we would get her a better life," said Nearnat. "Now she is divorced because he was a bad man. She refuses to get married again because then her ex-husband would take the children and now her younger sister is begging me not to go ahead with her marriage. I regret that my daughter was married young because now if she leaves the house her reputation will be ruined. The community all tease me."

Outside in the street a group of young men explain why they want to marry young brides. "Children need to have their rights but also you want to marry a girl who is much younger so she will stay young and beautiful when you are old. Also you can control her better and make sure she is not one of these girls who goes around wanting to be harassed," said Abdel Rahman, 17. His friend Youssef, 20, agrees. "There are many girls who just want to be harassed, walking around in the streets with their eyes uncovered."

Their views are not a surprise to Mona Hussein Wasef, 26, who works for Plan Egypt in Cairo. "For 18 days we were in Tahrir Square, side by side, men and women, educated and uneducated, rich and poor. Never have I felt so much solidarity. I was Egypt, we were all Egypt, fighting for freedom, shoulder to shoulder," she said. She is too fearful to attend any political demonstrations these days.

"Now we have never been so far apart, men and women. In such a short time, such a gulf. Now we are fighting just for the right to walk down the street without being assaulted. It is so hard, so shocking. To see the rights we had being ripped away and lost in the power struggle. To see us go backwards."

I WAS SOLD TO A SAUDI MAN – MY FUTURE IS RUINED





Rasmia Ahmed Emam was 17 when she was married to a 50-year-old stranger.

"My family is a big one so I had to sacrifice to support them. My dad went to a marriage broker to find a rich husband for me and she told us she had a Saudi man. He came and seemed to like me and gave my parents the money to build a roof on our house."

But the desperation of poor families combined with the acceptance of child marriage has created opportunities for unscrupulous marriage brokers trading young girls to sex tourists. Rasmia thought she was getting married but in fact she was kept in a hotel room for two weeks before "her husband" went home.

"I felt insulted, scared. I had a nervous breakdown. My father went to the broker but we had no proof of the marriage. She offered to marry me again. I refused. All my neighbours knew I was a prostitute, all my friends abandoned me. My future is destroyed. Now three girls in my street have been Saudi wives. All men are liars."

The phenomenon is becoming increasingly common in Cairo, says Mohammad Gazer, who has set up a charity, ACT, to warn families. "The taxi drivers bring men from the airport to the brokers. These girls are being traded and trafficked and dumped back home, their lives ruined.

"It is becoming clearer and clearer to Saudi men and other tourists that Egypt is the place for child marriage, for ignoring girls' and women's rights. It has got worse since the revolution and keeps getting worse every day."