'We're trapped in hell' Brutal truth of Italy's migrant crackdown

When she saw them, lined up at the road checkpoint, Marie sensed the situation might turn ugly. Four officers, each wearing the combat green of Tunisia's national guard.

They asked to look inside her bag.

"There was nothing, just some clothes," she says. For weeks Marie had traversed the Sahara, travelling 3,000 miles from home. Now, minutes from her destination - the north coast of Africa - she feared she might not make it.

Rape, beating and robbery The reality behind Italy's migrant policy as EU turns blind eye to Tunisian police

An armed officer lunged 28 towards her. Another grabbed her from behind, hoisting her into the air. By the road, on the outskirts of the Tunisian city of Sfax, the 22-year-old was sexually assaulted in broad daylight.

"It was clear they were going to rape me," she says, her voice wobbling. Her screams saved her, alerting a group of passing Sudanese refugees. Her attackers retreated to a patrol car.

Marie knows she was lucky. According to Yasmine, who set up a healthcare organisation in Sfax, hundreds of sub-Saharan migrant women have been raped by Tunisian security forces over the past 18 months. "We've had so many cases of violent rape and torture by the police," she says.

Marie, from the Ivory Coast city of Abidjan, knows others who describe rape by Tunisia's national guard. "We're being raped in large numbers; they [the national guard] take everything from us." After the attack, Marie headed to a makeshift camp in olive groves near El Amra, a town north of Sfax.

Migration experts say that tens of thousands of sub-Saharan refugees and migrants, encircled by police, are now living here. Conditions are described as "horrific".

Humanitarian organisations, aid agencies, even the UN, are unable to access the camp.