Hundreds of thousands of people of have fled a military offensive in northwestern Syria that has created one of the worst catastrophes for civilians in the country's long-running war. Many of the displaced have been forced to sleep in open fields and under trees in freezing conditions.

The weather has contributed to at least 10 deaths, including four who suffered hypothermia. A family of four died of suffocation in their tent, and two burned to death when their tent caught fire, according to Mohammed Hallaj, a coordinator for the area's Response Coordination Group.

Nizar Hamadi, 43, lost his brother and three other family members, including a three-year old. Their family was displaced multiple times, and they ended up in a settlement made up of tents stitched together with sticks and cloth.

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"It was God's destiny that it was really cold. The temperatures was no less then -8 or -9 (degrees Celsius, 15 degrees Fahrenheit) and this is rare in Syria," he said, speaking to The Associated Press from the Idlib town of Binnish.

He said his brother, Steif Abdel-Razak Hamadi, had moved north as Binnish also came under attack to set up his family's next shelter in Killi. On Tuesday, he set up a coal heater and by nightfall, as the fire died down, he moved it inside the tent and went to sleep with his family including his wife, two children and his grandchild.

"For the whole night, the heater was sucking out all the oxygen in the tent," Hamadi said.

When the son sleeping in another tent woke up and came to their tent, he found them all dead.

The government's Russian-backed assault on Idlib, the Syrian opposition's last stronghold, has uprooted more than 830,000 people since December 1, most of them fleeing toward safer areas near the border with Turkey, U.N. spokesman Stephane Dujarric said Friday.

At least 143,000 people have been displaced in the last three days.

The military campaign has also killed hundreds of civilians.

This Thursday, February 13, 2020 photo shows Syrian walking outside their tents at a displaced people camp near Turkish border, in Idlib province, Syria. Syrian Civil Defense White Helmets via AP

"Humanitarian needs are increasing exponentially," Dujarric said. "The ongoing emergency compounds the already dire humanitarian situation for people in the northwest, who have been made vulnerable by years of crisis, violence, economic downturn and, of course, multiple displacements," Dujarric said.

Terrified families piled on trucks and vehicles, sitting on top of mattresses and blankets, clogging sludgy rural roads in harrowing scenes of exodus that have been recurrent in Syria's conflict, now in its ninth year.

Around half the territory's population had already been displaced from other parts of Syria, so formal camps are full.

"It's cold, it's snowing and our life is terrible, we can't take this cold and neither can the kids," said a woman, who identified herself by her nickname Um Muhammad, who recently fled and was staying at a tent camp near the Turkish border.

"This life, what can I say? We are broken now. I am an old woman with kids, no one is taking care of us," she said, her face wrapped up in big black scarf against the cold.

The fighting has killed 1,700 people since last April, and the latest military campaign is disrupting aid operations, according to the United Nations. As of February 11, at least 72 health facilities have suspended services due to insecurity or mass displacement, it says.