GENEVA - The United Nations human rights chief urged the Iraqi government and US-led coalition on Tuesday to review tactics in Mosul to spare civilians he said were being deliberately put at risk by Islamic State.

At least 307 civilians have been killed and 273 wounded in western Mosul between Feb. 17 and March 22 as Islamic State fighters herd people into booby-trapped buildings as human shields and fires on those who flee, according to UN figures.

“This is an enemy that ruthlessly exploits civilians to serve its own ends, and clearly has not even the faintest qualm about deliberately placing them in danger,” UN High Commissioner for Human Rights Zeid Ra’ad al-Hussein said. “It is vital that the Iraqi Security Forces and their coalition partners avoid this trap,” he said in a statement.

“The conduct of air strikes on ISIL (Islamic State) locations in such an environment, particularly given the clear indications that ISIL is using large numbers of civilians as human shields at such locations, may potentially have a lethal and disproportionate impact on civilians,” Zeid said. The rules of war, as set out in the Geneva Conventions, require respecting the principles of precaution, proportionality and distinguishing between combatants and civilians.

Zeid also called on Iraqi and coalition forces to conduct transparent investigations into deadly incidents.

Meanwhile, UN chief Antonio Guterres called on Arab leaders Tuesday to set aside their differences to confront Syria’s six-year conflict, as he toured a Syrian refugee camp in Jordan.

“Arab unity is a very important element in order to allow this region to be stabilised and for... the Syrian refugees to find again a future that corresponds to their aspirations,” Guterres said.

Speaking on the eve of an Arab League summit hosted by Jordan, the UN chief said: “When Arab countries are divided, it has allowed others to intervene and to manipulate situations, creating instability, breeding conflict and facilitating the lives of terrorist organisations.” Guterres met with women and girls living in Zaatari, home to some 80,000 Syrian refugees.

Syria’s conflict began with protests against President Bashar al-Assad in 2011 but has turned into a brutal war pitting government forces, jihadists, rebels, and Kurds against each other.

The war has killed more than 320,000 people and forced 4.9 million people to flee their country.

In Jordan, where the UN High Commissioner for Refugees (UNHCR) says it has registered 630,000 Syrians, the government says it is hosting 1.4 million.

Jordan says the influx has strained its resources and has insisted it must screen newcomers to ensure they are genuine refugees and not jihadists seeking to infiltrate the country.

Guterres, who headed the UNHCR when the Syrian war broke out, said he remembered the first Syrian refugees arriving in Zaatari when it opened.

“How sad it is, how terrible it is, that today we still have Zaatari camp... and that the tragedy of Syrians is going on and on and on,” he said.

He urged the international community to step up humanitarian aid to the refugees in Jordan and other regional countries that are hosting them.

“I hope that if all countries that have an influence on the Syrian situation are able to come together these refugees that are living here artificially now for more than four years in this camp will be able to restart their lives again, to find jobs, to work, to have a normal life.”