Syrian warplanes bombed two rebel bases near the Turkish border on Monday sending hundreds of people fleeing across the frontier.
The attacks on the Free Syrian Army positions (FSA) in Atima and nearby Bab al-Hawa came a day before NATO and Ankara were due to start assessing where to station surface-to-air missiles on the Turkish side of the 900-km (560-mile) boundary.
Turkey, a big supporter of rebels fighting to oust Syria's President Bashar al-Assad, has repeatedly scrambled jets along the border. It has also responded in kind when shells from the conflict have landed inside Turkey, underlining fears Syria's 20-month-old revolt could spread to destabilize the region.
Ankara has rejected Syrian complaints that the NATO Patriots were "provocative" and stressed they would be used only to defend Turkish territory, not to create a no-fly zone inside Syria that rebels have long demanded as a way to neutralize Assad's massive air power.
Syrian planes dropped around six bombs on a rebel base near the Bab al-Hawa border crossing, said activists.