"They then dragged me to a room and raped me. One of them filmed the incident and warned to go public and publish the pictures if I do not co-operate," she said.
The latest accusation is likely to further stoke Shia-Sunni tensions already simmering over the earlier rape allegation.
Sabrine al-Janabi said she was raped by three Iraqi policemen last weekend, an allegation dismissed as false by the Shia-run government.
Nuri al-Maliki, the Iraqi prime minister, pardoned the three officers after a short investigation which lasted less than a day.
Al-Maliki insists the charge was fabricated by Sunni politicians to discredit the police and the ongoing security crackdown in Baghdad.
He announced a "reward" for the officers who were implicated.
Al-Maliki also fired a top Sunni official who called for an international investigation into the woman's allegations.
Ahmed Abdul Ghafour al-Samarrai, the head of the Sunni Endowment, a government body that caters to the needs of Sunni mosques and religious establishment throughout the country, was fired on Wednesday.
Al-Maliki's office gave no reason for dismissing al-Samarrai.
On Monday, al-Samarrai said the rape allegations proved the failure of US and Iraqi security forces to protect Baghdad's citizens.
Following his dismissal, al-Samarrai, speaking from Amman in neighbouring Jordan, said al-Maliki lacked the authority to fire him. He also reiterated his demand for an international investigation.
"We will continue to speak with courage, and we will not fear anyone but God," al-Samarrai said.
"I am not concerned about a job because the honour of Iraqi women is a thousand times more valuable than government jobs," he said.