UN says Syria is seeing its 'fastest growing displacement' since war began

More people have fled fighting in Syria over the past 10 weeks than at any other time in the nine-year-old conflict, and the city of Idlib, where many are sheltering, could become a graveyard if hostilities continue, two UN agencies said on Tuesday.

Syrian government forces are shelling their way northwards, backed by Russian airstrikes, driving people toward the Turkish border as they try to seize remaining rebel strongholds near Idlib and Aleppo.

Turkey, which backs the rebels and is fearful of additional refugees, has retaliated militarily, with displaced civilians caught in between.

"It's the fastest growing displacement we have ever seen in the country," Jens Laerke from the UN Office for the Coordination of Humanitarian Affairs (OCHA) said, adding that nearly 700,000 people had fled since December, mostly women and children.

Another 280,000 people could flee from urban centres if fighting continues, including from the city of Idlib, which is packed with people who have escaped fighting elsewhere and which has not yet seen a full military assault on its centre.

11 million people uprooted

"It has the world's largest concentration of displaced people and urgently need a cessation of hostilities so as not to turn it into a graveyard," Laerke added.

Of Syria's 17 million people, 5 million are living as refugees in the region, mostly in Turkey, and a further six million are uprooted within their own country.

Civilians are struggling to find shelter, amid harsh winter conditions with snow, rain and wind from Storm Ciara. Mosques are full and makeshift camps are overcrowded, said Andrej Mahecic, a spokesman for the UNrefugee agency.

"Even finding a place in an unfinished building has become nearly impossible," he told journalists in Geneva, describing the humanitarian crisis as "increasingly desperate."

LISTEN l 'An absolutely desperate situation': Syria displacement

OCHA has sent 230 trucks over two authorized border crossings in Turkey so far this month, containing food, water and hygiene equipment, Laerke added. Last month, 1,227 trucks were shipped in the biggest cross-border aid operation there since the operation started in 2014.

The UN Security Council renewed a six-month program delivering aid to civilians in January but stopped crossings from Iraq and Jordan to avoid a veto from Russia which backs Syrian President Bashar al-Assad. Aid workers say that is restricting their ability to help the displaced.

Deadly violence in Nairab, Idlib

In the latest fighting, rebels shot down a Syrian military helicopter in northern Syria on Tuesday, killing its crewin a fiery crash, while the government kept up its relentless bombing campaign on the opposition-held region, with an airstrike in which seven civilians died, activists and news reports said.

The Syrian helicopter gunship was shot down by insurgents amid fighting near the village of Nairab as rebels, backed by Turkish artillery, tried to retake it after losing it last week, according to opposition activists.

Associated Press video showed the helicopter spiralling from the sky and breaking up as fire poured from its fuselage, just before it crashed. Two bodies could be seen on the ground.

Turkey's official Anadolu news agency reported that the pilot and two others aboard were killed, while opposition activists reported that only two crew members were on board.

Hours later, a Syrian airstrike hit the city of Idlib, the provincial capital, killing seven people and wounding nearly two dozen others, according to SyriaCivil Defence, a volunteer organizationknown as the White Helmets. The Britain-based Syrian Observatory for Human Rights said the airstrike killed 12 civilians, half of them children, and wounded about 30.