HASAN SHAM CAMP, Iraq (Reuters) - Pushing his way through dozens of people, Iraqi teacher Umar Salah carries four bags containing 15 blankets and pots full of food through the gate of a camp overcrowded with civilians who fled Islamic State in Mosul.

A displaced Iraqi woman, who fled the Islamic State stronghold of Mosul, carries her belongings at Khazer camp, Iraq November 26, 2016. REUTERS/Mohammed Salem

Soldiers only occasionally open the gate to allow civilians to bring supplies to relatives inside, as authorities struggle to accommodate some 1,000 people fleeing the fighting every day since Iraqi forces launched a campaign to expel the militants.

U.S.-backed Iraqi government troops and Kurdish security forces have launched the biggest battle in Iraq since the 2003 U.S.-led invasion to drive Islamic State fighters from Mosul, the militant group’s last major bastion in the country, many times larger than any other city the fighters have held.

The United Nations is asking donors to fund winter kits for 1.2 million people -- preparing for a worst case scenario that much of the city’s population may have to flee. Seventy-two thousand have fled so far, and winter has brought freezing temperatures.

The Kurdish authorities are requiring fleeing civilians to stay in camps even if they have family outside, so that males can be checked for ties to Islamic State. Relatives crowded out front, bringing blankets and pillows.

“My relatives have ice on their tent at night,” said Salah, as he waited for his cousins and their five children to pick up the bags. “They don’t get enough blankets so I brought them from my house.”

Salah escaped Mosul for Kurdish-held Erbil, 60 km east of the city, when Islamic State swept through the area in June 2014. The rest of his family fled two weeks ago.

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Males who have been displaced have to hand over their ID cards on the day they arrive.

“I want to stay with my family in Erbil, but they keep us here,” said a young man, who gave his name only as Hisham, standing in front of a tent with his veiled wife and baby. “I have been waiting for three weeks.”

The two main camps, Hasan Sham Camp hosting 10,800, and the nearby Khazer Camp home to 29,000, are full.

The U.N. refugee agency UNHCR started work on Sunday on a another camp nearby, clearing the ground of landmines to set up 1,600 tents. Government workers are also setting up more blue tents at the Hasan Sham camp.

The United Nations has opened another camp in Tikrit south of Mosul, while near Tal Afar in the west, a flashpoint town where thousands of people have fled, another camp will be launched this week, according to refugee agency UNHCR.

Expecting a longer stay as the battle drags on, many families bring in stoves and kitchen utensils. With soldiers turning back most people at the camp gate, dozens threw their bags over the fence.

Parents were registering children to attend schools inside the camps, often their first opportunity for regular schooling in years.

“Children lost two years because schools were closed under Daesh (Islamic State) or taught only Islamic law,” said a teacher who gave his name as Ali.

Having himself fled Islamic State, he applied to work in camp schools. His own village is just 500 meters away, but the army has not opened it to civilians yet because the front line is still too close.

“The children need to go back to school while we wait here.”