Tens of thousands of Syrian Kurds swarmed across a bridge into neighboring Iraq's northern self-ruled Kurdish region over the past few days in one of the biggest waves of refugees since the revolt against President Bashar Assad began, AP quoted U.N. officials as saying Monday. The sudden exodus of around 30,000 Syrians amid the summer heat has created desperate conditions and left aid agencies and the regional government struggling to accommodate them, illustrating the huge strain the 21⁄2-year-old Syrian conflict has put on neighboring countries. The mostly Kurdish men, women and children who made the trek join some 1.9 million Syrians who already have found refuge abroad from Syria's relentless carnage. "This is an unprecedented influx of refugees, and the main concern is that so many of them are stuck out in the open at the border or in emergency reception areas with limited, if any, access to basic services," said Alan Paul, emergency team leader for the Britain-based charity Save the Children. "The refugee response in Iraq is already thinly stretched, and close to half of the refugees are children who have experienced things no child should," he said, adding that thousands of refugees were stranded at the border, waiting to be registered. The U.N. said the reason for this flow, which began five days ago and continued unabated Monday, is unclear. But Kurdish areas in northeastern Syria have been engulfed by fighting in recent months between Kurdish militias and Islamic extremist rebel factions with links to al-Qaida. Dozens have been killed.