CEYLANPINAR, Turkey - Forces loyal to Syrian President Bashar Assad bombarded the Ras al-Ain area on the border with Turkey on Sunday, days after the town fell to rebels during an advance that has sent thousands of refugees fleeing for safety.Helicopters circled above the town and opposition activists said they had strafed targets near the village of Tal Halaf.Turkey has already beefed up security on its southeastern border with Syria, in an area of the country where it is also fighting an emboldened insurgency by the Kurdistan Workers' Party (PKK).Increasingly critical of the failure of world powers to halt the war, Turkey is in discussions with NATO allies over the possible deployment of Patriot surface-to-air missiles to defend against any spillover of violence.The move could also be a step towards enforcing a no-fly zone within Syria to limit the reach of Assad's air power.An estimated 4 million Syrians to require aid by 2013The latest escalation along the Turkish border comes after a senior UN official on Friday warned that an estimated 4 million people in Syria will need humanitarian aid by early next year, up from the current 2.5 million whose needs the world is already failing to meet fully.John Ging, director of operations at the UN Office for the Coordination of Humanitarian Affairs (OCHA), painted a bleak outlook for civilians caught up in intensifying civil war between Syrian government forces and rebels."If the current rate of conflict continues at the current pace we can reasonably project that numbers in need to rise from 2.5 million to 4 million by the early new year," Ging told a news briefing after chairing the Syrian Humanitarian Forum."Every day our humanitarian colleagues on the ground are engaging with people who are ever more desperate, ever more fearful for their lives and for the lives of their families because of this conflict," he said.The Arab and Kurdish town of Ras al-Ain fell to the Free Syrian Army on Thursday in fighting that sent 9,000 fleeing in a 24-hour period, one of a largest refugee influxes into Turkey of the 19-month civil war.Tank rounds slammed into the western part of the town on Sunday and a Reuters reporter on the Turkish side of the border saw black smoke rising over the area.Rebels and forces loyal to Assad exchanged artillery fire and some rounds appeared to land just inside Turkey."It's a disaster over there," a man shouted to reporters as he crossed into the Turkish town of Ceylanpinar. Ambulances with sirens wailing ferried wounded people from the Turkish side of the border for treatment at a local clinic.With winter setting in, over 120,000 Syrians are now sheltering in Turkish camps, deepening alarm in Ankara.