Istanbul (CNN) Nearly a quarter of a million people in northwest Syria have been displaced over the past two weeks due to an escalation of violence in Idlib province , the country's last major opposition bastion, the United Nations has announced.

"As a result of hostilities, tens of thousands of families fled their homes in an effort to reach safety," the UN's Office for the Coordination of Humanitarian Affairs (UNOCHA) said in its latest situation report , published Thursday. "Between 12 and 25 December, more than 235,000 people have been displaced in northwest Syria."

The Syrian army, with support from Russian air power , has stepped up its attacks on the northwest province of Idlib, home to more than 3 million Syrians.

On Thursday, US President Donald Trump condemned the offensive and warned warned the Syrian regime and its allies against killing "thousands" of people in the province.

"Don't do it!" he wrote, accusing Russia, Iran, and the Syrian government led by Bashar al-Assad of "killing, or on their way to killing" the civilians.

The Syrian government has said that it is targeting terrorists in Idlib. But if the violence continues, even more civilians could be displaced in the coming weeks, international aid organizations have warned.

New wave of displacement

The mass displacement over the last two weeks has led to people being housed in mosques, garages, wedding halls, UNOCHA said.

But it warned that "the capacity to absorb people in need may surpass available places" and their displacement in the height of winter "is further exacerbating" the humanitarian situation.

Meanwhile, thousands of families are too scared to move, "fearing the risk of airstrikes and shelling along the routes," the report added.

CNN previously reported on airstrikes targeting one of the evacuation routes from the town of Maraat al Nouman -- one of the hardest hit towns in the recent escalation.

UNOCHA said the situation was compounded by a shortage of fuel for vehicles and the "ongoing emergency situation in northwest Syria that resulted in the displacement of an estimated 400,000 people between late April and late August 2019."

Turkish aid organization IHH told CNN they had erected a new tent site and are in the process of building new more permanent structures for the recent arrivals but more shelter is needed.

While there has been a slowdown in the movement of people with a brief lull in hostilities, many remain in need of urgent aid, IHH said.

Earlier in the week, a volunteer with the search and rescue organization the White Helmets described the situation in Idlib as a "disaster," with millions of people squeezed into a smaller and smaller area.

"People are leaving forcibly, you look at them and they look almost dead, they don't know where to go," Laith Al Abdullah, the White Helmets volunteer, told CNN in a phone call.

The sheer number of displaced people is overwhelming an already overstretched area. "It is crowded now to the point where people are sleeping on the streets and under trees ... People are terrified by the winter, we are getting a polar cold storm in few days, kids and women won't be able to stand it," he said.