Northwestern Syria faces a "major protection crisis" with more than 3 million people trapped in a war zone, the U.N. said Monday, warning about a possible bloodbath.

"There is a major protection crisis in northwest Syria. That is the fundamental issue," Mark Cutts, the U.N. Deputy Regional Humanitarian Coordinator for the Syria Crisis, told reporters in Geneva.

"More than 3 million civilians (are) trapped in a war zone in the Idlib area, and the fighting has been forcing them into a smaller and smaller piece of land close to the Turkish border," he said.

He noted that even as refugees from Idlib flock toward the border, Turkey already hosts more refugees than any other country in the world, totaling some 3.6 million.

While Turkey had said it does not want to see more refugees coming in, he added: "Turkey also supports the cross-border humanitarian operation."

"We have been talking with the Turkish authorities about ways of increasing the capacity of aid crossing at the border from Turkey into northwest Syria," Cutts told reporters.

"This a vital lifeline for the millions of people in northwest Syria," he added.

In January, the U.N. Security Council allowed a cross-border aid operation to continue from Turkey but closed crossing points from Iraq and Jordan due to opposition from Russia and China.

Cutts said he was "extremely concerned" about the continuation of the cross-border aid after June.

As Cutts stated, the U.N. sent 1,200 aid trucks into the area in January and has dispatched 700 more so far in February. "The reality is it is simply not enough. We're barely able to meet the needs of the people for the most urgent food rations and tents and blankets and winter items," he explained.

Cutts also said aid workers were "overwhelmed," some warehouses had been looted and the fighting had damaged some 77 hospitals and other medical facilities.

The U.N. was trying to double aid deliveries across a border crossing from Turkey from 50 to 100 trucks a day, he added.

Turkey is already hosting more than 3.6 million Syrian refugees. It says it cannot take more and was hoping to create a "safe zone" along the border to resettle them but the renewed spike in violence has endangered that plan.

The current wave of displacement is the worst in Syria's nine-year conflict, with nearly a million people, more than half of them children, uprooted since December.

The fighting is now getting "dangerously close" to the area where more than a million are living in tents and makeshift shelters in an "extremely alarming situation" due to airstrikes and shelling, Cutts explained.

He said if people continue to move into the area, "We are no doubt going to see a real bloodbath, a real massacre of civilians in that area."

Some 400,000 people were forced to flee their homes last summer, followed by a further escalation beginning in December, he said. More than 900,000 people were forced to flee their homes.

"Since then, the numbers of displaced people are staggering. During the nine years of this war, about 12 million Syrians have been forced to flee their homes," he said.

About 5.5 million are refugees outside of Syria, and about 6.5 million are internally displaced.

"So huge figures and a huge protection crisis. Our biggest concern is the widespread and systematic targeting of densely populated civilian areas," he said. Entire cities and towns and villages were emptied, he added.

Idlib, near Turkey's southern border, falls within a de-escalation zone laid out in a deal between Turkey and Russia in late 2018.

The Syrian regime and its allies have consistently broken the terms of the agreement, launching frequent attacks inside the territory where acts of aggression are expressly prohibited.

A months-long offensive by Russia-backed Syrian regime troops against opposition groups backed by Turkey in northwest Idlib has seen hundreds of thousands of people flee the violence.

Turkey has called for an immediate halt to the attacks on Idlib, and for the cease-fire to be followed, warning that if the attacks do not stop, it will take action.

"Huge numbers of hospitals and schools and marketplaces and bakeries and water stations have been hit by airstrikes and shelling in the last few months. And there's a population now which is terrorized and traumatized and living in fear. People have been fleeing in fear, to the border area," Cutts said.

As a result of the escalation, he said the U.N. was revising its funding appeal for the crisis from $330 million to $500 million, adding that there was a shortfall of about $370 million.

5 more civilians killed

Most recently, five civilians were killed in Russian airstrikes backing Syrian regime forces as they chipped away at the country's last major opposition bastion in fighting that cost dozens of lives Monday, a war monitor said.

The Syrian Observatory for Human Rights said the air raids hit the Jabal al-Zawiya area on the edge of the northwestern province of Idlib.

In fighting on the ground, regime forces gained ground in the southern part of Idlib, the U.K.-based monitor said.

They seized 10 towns and villages south of the M4 highway linking the coastal regime stronghold of Latakia to the regime-held second city Aleppo since Sunday, it said.

Observatory chief Rami Abdel Rahman said the regime aimed to wrest back control of stretches of the M4 still under the control of opposition groups.

That would require operations against the towns of Ariha and Jisr al-Shughur, both along the M4.

Loyalist forces have already taken back control of another key commercial artery running through northwest Syria – the M5 that connects the capital with Aleppo. They have also secured the region around the northern city, a major pre-war industrial hub. Regime forces have since December clawed back chunks of the Idlib region, forcing close to a million people to flee their homes and shelters amid the bitter cold.