Paramilitary militias and government forces in Iraq were accused of committing serious human rights violations against civilians escaping Isis-controlled Mosul in a new report from Amnesty International.

The report 'Punished for Daesh's crimes': Displaced Iraqis abused by militias and government forces highlighted widespread revenge attacks and discrimination faced by Sunni Arabs suspected of working with Isis.

Battle for Mosul
Displaced people who fled Mosul sit inside a tent at a refugee camp in Duhok, Iraq Safin Hamed/AFP

"After escaping the horrors of war and tyranny of Isis, Sunni Arabs in Iraq are facing brutal revenge attacks at the hands of militias and government forces, and are being punished for crimes committed by the group," said Philip Luther, research and advocacy director for the Middle East and North Africa at Amnesty International.

"As the battle to retake Mosul gets underway, it is crucial that the Iraqi authorities take steps to ensure these appalling abuses do not happen again. States supporting military efforts to combat Isis in Iraq must demonstrate they will not continue to turn a blind eye to violations."

The predominantly Shi'a militias involved in abuses, known as the Popular Mobilisation Units, became officially designated part of the Iraqi forces in February 2016.

All males considered to be in fighting age, some as young as teenagers, fleeing Isis-controlled areas undergo security by Iraqi authorities and the semi-autonomous Kurdistan Regional Government. Amnesty International denounced the process as "opaque and often deeply flawed," with some people detained for weeks or months, without being referred to court and often subjected to human rights abuses.

The study is based on interviews with more than 470 former detainees, witnesses and relatives of those killed, disappeared or detained, as well as officials, activists, humanitarian workers.

Detainees told Amnesty International they were suspended in stress positions for long periods, given electric shocks, beaten brutally or were taunted with threats that their female relatives would be raped. Many said they were tortured to "confess" or to provide information on Isis and other armed groups.

Kurdish authorities denied the findings

Amnesty said they shared the report findings with the Iraqi and Kurdish authorities in September, but the the Iraqi authorities did not reply, while the Kurdish authorities denied the findings.

The NGO called for an independent investigation into the abuses. "Failure to do so will allow a vicious cycle of abuse, repression and injustice to continue and raises serious fears about the safety of civilians still in Mosul," said Luther.

Other humanitarian workers share concerns over the protection of civilians escaping the embattled city. Khalil Sleiman, World Vision's response manager for northern Iraq, said there may be issues related to the identification and registration. He warned against separating families, to protect them from further trauma.

Sleiman said: "We're already supporting half a million people who fled Mosul when it was first occupied over two years ago. We're now poised for another massive influx of children and families who will have been through horrific experiences most of us could never imagine.

"We call for humane treatment at every stage of the process of the Mosul operation – including screening when boys as young as 14 may be separated from their families."