Iraqi security forces and allied militias burned and looted homes and destroyed entire villages in territory retaken from the Islamic State (IS) extremist group, Human Rights Watch said on Wednesday.

These violations took place after government troops and militias broke a siege on the town of Amerli in August last year with the help of US and Iraqi airstrikes. Businesses, residences, public buildings and even mosques in the area were subsequently razed, possessions of Sunni residents looted and entire properties and villages destroyed using explosives and demolition equipment, according to evidence gathered by HRW.

'Iraqis are caught between the horrors ISIS (IS] commits and abusive behavior by militias, and ordinary Iraqis are paying the price.'

Satellite images of some of the affected villages shows widespread destruction caused by demolition and arson inflicted after the fighting had finished.

IS had laid siege to Amerli, in Salahuddin province, for three months following its shock offensive in June when it seized a large swathe of northern Iraq. Government forces backed by Shia militias, alongside peshmerga fighters from the Kurdish Regional Government, pushed IS back with the help of air support.

After the operation was over, however, troops and militias targeted Sunni villages and neighborhoods in and around Amerli from September through to November, HRW concluded after visiting the scene, conducting interviews with witnesses and victims and analyzing photos, video footage and satellite imagery. Many of the villages targeted were ones which IS had moved through or used as bases.

Witnesses, including peshmerga officers and local sheikhs, described militiamen looting items of any value, such as electrical goods, clothing, and even wiring from houses before burning them to the ground. Militias involved included parts of the Badr Organization — an armed political movement closely associated with Iran — Kata'ib Hezbollah, and Asa'ib Ahl al-Haq, according to local residents. 47 villages were targeted, according to peshmerga sources cited by HRW.

IS has been involved in widely publicized abuses, including numerous massacres that have been described as crimes against humanity.

Shia militias have played a major part in the Iraqi fight against IS, filling the gaps after the spectacular collapse of a significant part of the regular armed forces during IS's June offensive. They are now more powerful and influential than ever and lawmakers have allowed them to boost their strength and numbers. In some cases, this seems to have been accompanied by a return to the campaigns of kidnappings and killings last seen during the brutal sectarian violence that almost tore Iraq apart in 2006 and 2007.

Rights groups have said the militias operate outside the law with little or no accountability and there have been a number of documented allegations of summary killings and other abuses in Iraq, accelerating massively since the rise of IS.

Prime Minister Hayder al-Abadi has previously pledged to bring all armed groups under state control or oversight.

HRW deputy Middle East and North Africa director Joe Stork called on him to make good on his promise. "Iraq can't win the fight against ISIS's atrocities with attacks on civilians that violate the laws of war and fly in the face of human decency," he said, using the alternative name for the Islamic State. "Militia abuses are wreaking havoc among some of Iraq's most vulnerable people and exacerbating sectarian hostilities."

He added that countries providing assistance to the Iraqi government, including the US and Iran, should back these calls. "Iraq clearly faces serious threats in its conflict with ISIS, but the abuses committed by forces fighting ISIS are so rampant and egregious that they are threatening Iraq long term." Stork said. "Iraqis are caught between the horrors ISIS commits and abusive behavior by militias, and ordinary Iraqis are paying the price."

The report comes as a 30,000-strong mixed force made up predominantly of troops and allied Shia militias comes close to pushing IS out of Tikrit, also in Salahuddin province, where some Sunni tribes and supporters of deceased former dictator Saddam Hussein's Baath Party in the area sided with IS against the government last year.

Regional Shia powerhouse Iran is heavily involved in the operation, raising concerns about the risk of increased sectarian tensions as a result.

IS kidnapped then executed more than 1,000 predominantly Shia recruits from the Camp Speicher military base close to Tikrit in June and Shia militias, which often accuse local Sunni tribes of involvement in the killings, vowed revenge. Transport minister and Badr Organization head Hadi al-Ameri made the link explicit in the initial stages of the Tikrit assault when he said the city's residents should leave their homes to allow pro-government forces to "wrap up the battle of the revenge for Speicher."

Around the same time, however, Abadi urged civilian lives and property to be protected, seemingly referring to fears that Tikrit's Sunni civilians could be targeted in reprisal attacks.