Omar Salem Shehab tells of torture at hands of notorious Iraqi police unit and says US forces were involved in his capture

During the foreboding months of 2005, one police unit struck more fear into Iraqis than the entire occupying US army. They were known as the Wolf Brigade.

Brutal even by Iraqi standards, their soldiers and officers seemingly answered to no one. They were seen as indiscriminate and predatory. The unit's reputation had been known Iraq-wide and results of their numerous raids are still bogged down in Iraq's legal system.

But the full range of their abuses and close co-operation with the US army remained in the shadows until the WikiLeaks disclosures showcased them in stark detail.

A visit from the unit to any neighbourhood was sure to bring trouble – as it it did for Omar Salem Shehab on 25 June that year.

"We were at home that night," Shehab recalled this week. "We were three brothers sleeping above my ice-cream shop. We were woken by soldiers entering our house by force. They came with Americans. They said we were wanted and produced a document. The Americans took our pictures, then the soldiers we now knew were the Wolf Brigade took us to the Seventh Division camp [of the Iraqi army]."

Shehab and his brothers lived in Dora, in Baghdad's south, a lethal enclave of the city that was rapidly deteriorating into chaos. Like most of Dora's residents, they are Sunni Muslims.

The trio were at the army camp for a day, then transferred to Baghdad's main prison, known as Tsferrat.

"We were tortured all the time, he said. "We were never investigated, just tortured. The commander of the Wolf Brigade, Abu al-Walid was one of the torturers. My brother had a kidney problem and they continued to torture him without giving him medicine.

"He died after a month and the doctor wrote 'kidney failure' as a cause of death, despite his body being covered with torture marks. When he died, they let me and my other brother out. I later learned that another man we had met in prison, Khalid Hussein, had also died."

Torture and death seemed synonymous with the almost exclusively Shia unit, which was tasked with rooting out Sunni insurgents from post-Saddam Iraq. As security unravelled across the country, they were often seen alongside US forces, particularly in Baghdad and Mosul.

Earlier in 2005, they had swept into Mosul with the US army in support. Muataz Salah Ahmed, now 40, was working in the al-Mas hotel that January when the men in the distinctive red berets and balaclavas burst through the doors.

"They arrested us all," he said. "There was an Iranian officer, his name was Ali. Many other officers with him were proud to tell us that they were not police, but Wolf Brigade. They said they had come from Baghdad to arrest us because we supported Saddam and deserved to be executed.

"One officer threatened to rape my wife. He tore at her dress and four of my colleagues were killed in front of my eyes. They drilled holes in my legs and arms and did all manner of things to me. They took me and around 1,500 other prisoners to a basement inside the police commander's headquarters."

The unit stayed in Mosul for five months. Ahmed remained in prison for eight months, before being released by a court without conviction.

"I have many documents proving who they were and what they did to me," he said. "Twelve families have complained against the general in charge of the unit; his name was Khalid. But they were the government, so what can be done about them?"

The Wolf Brigade unit was formed in late 2004, drawing many recruits from the impoverished Shia slums of Sadr city. By late 2005, it was around 2,000-strong and roaming the country with impunity. The unit notionally answered to the then interior minister, Ibrahim al-Jafari, who became prime minister in April 2005 for 12 months as sectarian carnage spiralled out of control.

When Nouri al-Maliki replaced Jafari as prime minister, he pledged to crack down on the Wolf Brigade and any other units seen to be carrying out sectarian agendas. By then, most of its leaders had fled or been killed.

Questions have endured in the ensuing five years about the extent of US co-operation with the unit and whether US forces knew of the scale of their abuses.

"The Americans were there," said Shehab. "They weren't just witnesses. They were part of the operation against us."

Additional reporting: Enas Ibrahim