The United Nations Humanitarian Affairs office warned on Monday that nearly a million Syrian civilians from northwest Idlib province had been displaced in a Russia-backed offensive there by dictator Bashar al-Assad that began in December.

Idlib is the last stronghold of the anti-Assad rebel movement in the country. Assad has been at war with the rebels since 2011 and has been repeatedly accused of using chemical weapons against civilians and other human rights atrocities to cement his control over regions that oppose his rule. Conversely, rebel groups have faced allegations that they have cooperated with Sunni jihadist organizations, as the anti-Assad movement largely consists of Arab Sunnis opposed to the Shiite Alawite rule in Damascus.

While the struggle between Assad and Sunni rebels lies at the heart of the Syrian Civil War, as many as ten different factions have participated in violence in the country during the war, often unrelated to Assad such as the failed establishment of the Islamic State caliphate in Raqqa or clashes between the northern Syrian Kurdish People’s Protection Units (YPG/YPJ) and the Turkish military. Turkey claims to oppose Assad’s rule but has instead focused its energy on fighting the Kurds, who have not had any significant interaction with Assad’s army and instead largely contributed to the demise of ISIS.

The vacuum left by the fall of ISIS in the country has allowed Assad, along with allies Iran and Russia, to focus on attacking Idlib.

“The violence in north-west Syria is indiscriminate,” Mark Lowcock, U.N. Humanitarian Affairs chief, said on Monday. “We are now receiving reports that settlements for displaced people are being hit, resulting in deaths, injuries and further displacement.”

Refugees from the region “are traumatized and forced to sleep outside in freezing temperatures because camps are full,” he noted. “Mothers are burning plastic to keep children warm … babies and small children are dying because of the cold.”

Lowcock added that schools, hospitals, and other critical infrastructure has been destroyed. Exposure to nature while fleeing also leaves open the potential of a significant public health crisis in the event of disease spreading, he added.

He estimated that 900,000 people had been displaced since December 1. A week ago, the number of displaced in the region stood at 690,000 since December 1, according to the U.N. Office for the Coordination of Humanitarian Affairs, which estimated it was the largest number of displaced people in a single period of the Syrian Civil War. The sum is particularly jarring given that the U.N. estimates the Idlib region is home to 3 million people.

Lowcock urged U.N. Security Council action and a ceasefire to protect civilians.

Anadolu Agency, the state news agency of anti-Assad Turkey, claimed this week that the number was much higher – nearly 2 million displaced from Idlib since January. Anadolu claimed that rebels and Assad troops had declared a ceasefire recently that Assad had not respected; President Recep Tayyip Erdogan has threatened more military action against Assad in the near future.

As of this week, the United Nations estimates that over 5.6 million people have left Syria since the war began in 2011. Another 6.6 million are internally displaced, meaning they have lost their homes to the war and are either living homeless in cities or living in overcrowded refugee camps. The vast majority of those, over 3 million, who have left the country have fled to Turkey. Others in the new wave of displaced have fled to Manbij, Syrian Kurdistan. Local forces affiliated with the Kurdish fighters there have reported numbers too large to count of incoming refugees this month.

The Russian government has previously responded to United Nations reports on its atrocities in Syria by dismissing their information as false.

“They say the particular date a school or a hospital was destroyed in a particular region. They give coordinates. Our people start to double-check this and they find that there is no hospital with such coordinates, there is no school with such coordinates and the day which is mentioned by the U.N. humanitarian agencies, on this day, the Russian air force did not act at all,” Russian United Nations representative Gennady Gatilov complained in August, in response to yet another U.N. report accusing Moscow of helping Assad attack civilians. Gatilov claimed that biased NGOs on the ground provided the U.N. with misinformation.

This week, Russia has focused instead of accusing the United States of human rights violations.

“The oil fields … are controlled by the U.S. There’s shameless, impudent pillage of the wealth that belongs to Syria and the Syrian people taking place,” Defense Minister Sergey Shoigu claimed in Rome this week, referring to territories liberated from the Islamic State and managed by Syrian Kurdish groups.

The Assad regime’s state propaganda outlet, the Syrian Arab News Agency (SANA), claimed that, rather than terrorizing civilians, Assad has instead created a “humanitarian corridor” in Idlib for those who wish to leave.

“SANA reporter said that tens of citizens, most of them women, children, and elderly persons, exited through the humanitarian corridor established by the Syrian Arab Army west the liberated city of Ma’arat al-Nu’man, coming from the areas where the terrorists are positioned,” the outlet reported. SANA uses the term “liberated” to refer to cities under Assad control.

SANA also claimed Assad was providing medicine and food.

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