A trickle of people passes through a normally busy border crossing in the mountains of northern Iraq. “It’s a big prison over there,” one Iranian woman says, gesturing to the hulking gate that marks the border with Iran’s Islamic Republic, which has been convulsed by protest for over two months.

A portrait of the founder of Iran’s clerical regime, Ruhollah Khomeini, looms against a backdrop of rolling hills studded with streetlights. Snatches of travelers’ muted conversations punctuate an eerie silence.

Fear of indiscriminate arrest has made many reluctant to risk the journey. Some of the few who cross say the noose is tightening: protesters gunned down, curfews in the border villages and nighttime raids on homes.

In hushed tones, they speak of female protesters in particular, and the horrors they say some have endured in Iran’s notorious detention facilities.

Iran’s government has closed the country off to non-accredited foreign journalists, regularly shuts down the internet and suppresses dissidents' voices with mass arrests. An extreme climate of fear prevails in Iran as the crackdown intensifies.

One Kurdish-Iranian woman, whom CNN is calling Hana for her safety, says she both witnessed and suffered sexual violence while detained. “There were girls who were sexually assaulted and then transferred to other cities,” she said. “They are scared to talk about these things.”