CEYLANPINAR, Turkey — A Syrian warplane bombed the rebel-held town of Ras al-Ain on Monday, just yards from the Turkish frontier, sending scores of civilians fleeing for safety into Turkey.

Helicopters also strafed targets near the town, which fell to rebels on Thursday during an advance into Syria's mixed Arab and Kurdish northeast. There was no word on casualties.

The jet struck within yards of the border fence that divides Ras al-Ain from the Turkish settlement of Ceylanpinar, sending up plumes of black smoke.

A Reuters reporter in Ceylanpinar said the plane flew right along the border and appeared at one point to have entered Turkish airspace.

It was not clear what the bomb struck, but scores of civilians fled the area, scrambling over the fence into Turkey.

To Ankara's alarm, some 9,000 Syrians arrived in one 24-hour period last week, swelling to over 120,000 the number of registered refugees in Turkish camps, with winter setting in.

Turkey is becoming increasingly concerned about security along its border with Syria, in an area of the southeast where Ankara is also fighting an emboldened Kurdish insurgency.

Turkey says it is talking to its NATO allies about the possible deployment of Patriot surface-to-air missiles to guard against a spillover of Syria's 19-month-old conflict.

Such a move could also be a prelude to enforcing a no-fly zone in Syria to limit the reach of President Bashar al-Assad's air power, although Western powers have steered clear of this.

Turkish police fired tear gas and water cannon to keep people on the Turkish side away from the border fence. In Ceylanpinar, anxious residents crowded outside a teahouse to watch the bombing.

"I thought the Turkish government said it wouldn't allow these helicopters to come so close to the border," said one Turk who declined to be named. "Look, they're coming inside our border."

Ras al-Ain, 375 miles from Damascus, is part of Syria's northeastern oil-producing province of Hasaka, home to many of Syria's million-strong Kurdish minority.

Syrian Kurds have largely stayed away from the anti-Assad revolt and fear that the mostly Sunni Muslim Arab rebels will ignore their aspirations for autonomy in any post-Assad era.