Aid agencies were struggling to cope with a tide of half a million refugees fleeing Isis militants yesterday as the United Nations launched one of its biggest humanitarian operations.

The first 100-tonne shipment of aid arrived at Arbil airport in Iraqi Kurdistan, destined for thousands of Yazidis and other religious minorities traumatised by the jihadist onslaught.

Aid workers who interviewed the refugees have heard harrowing stories of their ordeal at the hands of Isis.

“Almost every individual we have spoken to has given a horrific account of violations they or members of their family or community have witnessed or experienced,” said Ibrahim Sesay, Unicef’s child protection specialist.

One 16-year-old girl told interviewers that she was rounded up with other women and girls who were selected to provide sexual services under a forced temporary marriage, the agency said.

The task of helping the refugees in Iraqi Kurdistan, where aid workers must contend with airstrikes, shifting front lines, government cash shortages and a transient and traumatised population, is daunting.

“We’re still in emergency mode,” said Natalia Prokopchuk of the UNHCR. “Population movements have just stabilised in the last few days and camps have to be built.”

Several of those camps-in-progress are in the far north of the country, near Dohuk, where nearly 200,000 Yazidis from the Sinjar region have swelled the number of displaced people to well over half a million.

In Bahirka camp on the outskirts of Arbil, the organisers were overwhelmed. The new arrivals were dust-caked and thirsty in 44-degree heat, and the plumbing was broken.

“Back at my house, I have a better space for my dog,” said Ayad Younis, a father of four who traded his house for a tarpaulin shack. “I’ve got two options: surrender to Da’ash [Isis] or live this way,” he said. He looked around and sighed. “We just didn’t see this coming.”