The United Nations said 235,000 civilians had fled their homes in the rebel-held northwestern Syria this month as a result of a military showdown there.

The UN Office for the Coordination of Humanitarian Affairs (OCHA) said the exodus had taken place between December 12 and 25. 

Most people had fled the city of Maarat al-Numan, towns and villages in southern Idlib province, Idlib city, and camps along the Syrian-Turkish border, OCHA said.

"With the latest escalation of violence in northwest Syria, civilians in Idlib governorate are again suffering from the devastating consequences of hostilities," it said.

OCHA said Maarat al-Numan and the surrounding countryside "are reportedly almost empty."

Thousands of families were also reported to be too frightened to move, fearing air strikes and shelling.

U.S. President Donald Trump on Thursday warned Russia, Syria, and Iran against violence in Idlib Province of northwestern Syria, the stronghold of Syrian rebels.

"Russia, Syria, and Iran are killing, or on their way to killing, thousands of innocent civilians in Idlib Province. Don't do it!" Trump tweeted in the morning.

Trump added in his tweet that "Turkey is working hard to stop this carnage," without providing further details.

Forces loyal to the Syrian government, backed by Russian airstrikes, have launched a fresh round of fierce offensives in Idlib to capture the last rebels' stronghold in the war-torn country.

Moscow and Damascus deny the claims, saying they are fighting jihadist militants.

The Syrian army said in a statement on Tuesday that it will continue the military operation until "liberating" Idlib Province from "terrorists," state news agency SANA reported.

The statement urged civilians in Idlib to stay away from the rebel positions, noting that the army will "liberate" Idlib while preserving the lives of the civilians.

Turkish presidential spokesperson Ibrahim Kalin said Tuesday evening that Ankara asked Moscow to establish a ceasefire in Idlib after the region has seen an uptick of violence in recent days.

Turkey and Russia agreed in September 2018 to turn parts of Idlib into a de-escalation zone in which acts of aggression are prohibited.

However, such deals exclude the ultra-radical rebels who are affiliated with the al-Qaida and branded as terrorist groups by the United Nations.

Idlib hosts some three million people including many displaced by years of violence in other parts of Syria.

The Russian and Syrian advance toward Idlib is also piling pressure on Turkey, which has a presence in the area and is seen by many civilians as a protector against Russian strikes.

Turkish President Tayyip Erdogan said his country cannot handle a fresh wave of migrants from Syria, warning that Europe will feel the impact of such an influx if the bombing is not stopped.

(With input from Xinhua, Reuters)