Turkey has floated the idea of a "safe zone" to be set up for civilians under foreign protection as fighting has intensified in a 17-month-old uprising against President Bashar al-Assad.
Up to 5 000 refugees a day have been crossing into Turkey over the past two weeks while the pace of refugees arriving at a camp in northern Jordan has doubled, heralding what could be a much bigger movement there, the UN said.
Although there is no sign divided world powers are ready to back a buffer and no-fly zone, as rebels and aid organisations would like, UN Security Council foreign ministers are expected to discuss the idea at a meeting on Thursday.
While Turkey could in theory create a buffer zone itself, it has said it is reluctant to go it alone.
Already hosting more than 80 000 refugees, Turkey has warned it could run out of space if the number goes above 100 000.
"We are already looking at potentially up to 200 000 and are working with the Turkish government to make the necessary plans," Sybella Wilkes, spokesperson of the UN High Commissioner for Refugees (UNHCR), said in Geneva.
Turkey fears the presence of refugees fleeing a conflict with a sectarian dimension could worsen its own tensions as well as straining resources.
Turkey will open four new camps for Syrian refugees by next week, bringing its capacity to 120 000 people, its disaster management agency said, but thousands remain stuck inside Syria.
"We will be asking the United Nations to be more active in terms of helping the Syrians on their side of the border," said one Turkish official, who declined to be named. He complained that Turkey had received little help so far.
Relations between Turkey and Syria have deteriorated sharply during the uprising. Syria accuses its neighbour, hosting rebel forces, of backing 'terrorist' infiltration and shot down a Turkish plane in June.
The refugee flow to Turkey has grown as fighting has worsened around Syria's biggest city, Aleppo, split between rebels and Assad's forces in a street-by-street battle that has ground on for weeks.
Heavy fighting has also returned to districts around Damascus, one month after rebels were driven back from the centre of the capital. Twelve people were killed by a car bomb at a funeral in Damascus on Tuesday, state television said. Activists said the attack targeted Assad supporters.
At least 18 000 people have been killed and 2.5-million Syrians are in need of aid or assistance, the United Nations says. More than 200 000 refugees have registered in neighbouring countries, though significantly more have left Syria.
At the Azaz-Kilis crossing, the main route into Turkey from Aleppo, Syrians described dire conditions for refugees still trapped on the other side of the border.
"We saw people sitting on the street and sleeping. They don't have a toilet. It's very bad … No food. Children in the street," said Juma'a Handawi, shortly after crossing.
Pick-up trucks crammed with people, mattresses, clothes and wooden furniture ferry refugees to the border. Rebel fighters draped with ammunition belts and carrying automatic rifles loiter among women and children waiting to cross.
Ankara fears a mass influx on the scale of the 1991 Gulf War, when half a million people poured into Turkey.
French Foreign Minister Laurent Fabius, who will chair Thursday's UN meeting, said on Monday a no-fly zone may become an inevitability if refugee numbers continue to soar, while US Secretary of State Hillary Clinton said in Turkey this month that all measures including a no-fly zone were on the table.
But no UN Security Council member has formally proposed such a measure and there are legal and practical obstacles to establishing such a zone, diplomats say, as well as strong opposition from Russia and China.
"At the moment we're not expecting much," said one French diplomatic source of the meeting on Thursday.
Many of the refugees in Turkey and other neighbouring states have been housed in schools and sports centres but, with the academic term due to begin, they are being moved on.
Refugees sheltering at schools in Marj, a town in Lebanon's Bekaa Valley, were told to find somewhere else to stay after the education ministry ordered all schools to be cleared by September 2 for the registration of students, a local official said.
Men, women and children stood in the street in front of one school with their bags and suitcases, some unsure where to go.
"I will look for a house to rent and if we can't find one, we will have to go back to Syria, and whatever will happen is going to happen," said Abu Amar, who fled from fighting in the Damascus district of Kafr Souseh last month.
Activists said the new wave of refugees to Jordan may have been caused by shelling on houses in the southern town of Busra al-Sham that killed at least 15 women and children last week.
Jordan called for help with the refugee influx.
"We are being burnt by the impact of this crisis in a direct manner," Minister of State for Information Samih Maaytah told Reuters. – Reuters