(New York) – Iraqi forces fighting to recapture the city of Tikrit from the extremist group Islamic State (also known as ISIS) should protect civilians from revenge attacks by pro-government militias. In accordance with the international laws of war, all fighting parties should take all feasible precautions to minimize harm to the civilian population.

Human Rights Watch has documented numerous atrocities against Sunni civilians by pro-government militias and security forces after they retook other towns. Amid reports that ISIS has taken civilians captive as human shields, forces that capture ISIS fighters and take suspected ISIS supporters into custody should promptly transfer them to official Justice Ministry facilities to reduce the risk of summary executions, revenge killings, or other abuses, Human Rights Watch said.

“All commanders in Tikrit need to make sure that their forces protect civilians and allow them to flee the combat zone,” said Joe Stork, deputy Middle East and North Africa director at Human Rights Watch. “Past fighting raises grave concerns that Tikrit’s civilians are at serious risk from both ISIS and government forces, and both sides need to protect civilians from more sectarian slaughter.”

On March 2, 2015, an Iraqi military force along with volunteers from the quasi-governmental Hashd al-Shaabi, or Popular Mobilization Committees, and pro-government militias began an offensive to retake Tikrit.

Iraqi officials have recently made statements that raise concerns about possible retaliatory attacks in Tikrit, Human Rights Watch said. In a speech to parliament on March 2, Prime Minister Hayder al-Abadi said: “There is no neutrality in the battle against ISIS. If someone is being neutral with ISIS, then he is one of them.” While Abadi also urged government forces to exercise the “utmost care in protecting civilian lives and property” in the fighting, in the past they have shown little respect for civilians’ lives, Human Rights Watch said.

Hadi al-Ameri, former transport minister and leader of the Badr Organization, a leading Shia militia, told Tikrit residents over the weekend to flee so that his forces could “wrap up the battle of revenge for Speicher,” media reported. The reference apparently was to the killing by ISIS of hundreds to thousands of Shia recruits taken prisoner when ISIS overran a military base near Tikrit in June 2014.

Human Rights Watch, using photo analysis, satellite imagery, and witness testimony, documented the massacre at Camp Speicher and determined that ISIS killed at least 770 prisoners at five execution sites. ISIS claimed it slaughtered 1,700 people.

On March 1, 2015, the Institute for the Study of War said it had received reports that ISIS fighters were holding “an unspecified number of civilians as human shields” in Tikrit. Government forces and pro-government militias should ensure that everyone in their custody, whether ISIS fighters, civilians, or civilians press-ganged by ISIS to fight for it are treated humanely, according to the laws of war.

Human Rights Watch has documented repeated abuses against civilians in areas that Iraqi security forces and militias have retaken from ISIS since it took control of the northern city of Mosul, Iraq’s second largest city, last June. They include mass killings of prisoners and what appears to have been sectarian retaliation against Sunni civilians. Human Rights Watch also documented militias’ alleged war crimes against civilians in Diyala province after battles against ISIS in the area.

That same month, Iraq’s Grand Ayatollah Ali al-Sistani condemned attacks on civilians and their property after fighting, and issued guidelines to pro-government fighters. He called on them to protect civilians during combat and ordered fighters to observe Islam’s rules of war.

Much of Tikrit’s pre-war population of roughly 260,000 has fled, but an unknown number of civilians – particularly those too poor or too elderly to flee – remain in the city and its outskirts, according to media reports.

All parties to the armed conflict in Iraq are required to abide by the laws of war. People who commit serious laws-of-war violations deliberately or recklessly are subject to prosecution for war crimes. Attacks that do not discriminate between combatants and civilians, or that can be expected to cause harm to civilians disproportionate to the expected military gain, are unlawful. Forces must take all feasible steps to protect civilians under their control from attacks and avoid deploying in densely populated areas.

The laws of war require treating everyone in custody humanely, and protecting them from torture or other ill-treatment. Looting and destruction of property not being used for military purposes is prohibited.

In addition to Tikrit, ISIS holds large swathes of territory throughout Iraq, including Mosul and much of western Anbar province.

“The warring parties throughout Iraq need to protect civilians caught in the fighting and not commit looting or revenge killings,” Stork said. “How the government fights this war will have an important impact on Iraq’s future.”