“The Syrians are getting killed in a war between Saudi Arabia and Iran,” he said, referring to regional supporters of the two sides.

Image Credit... The New York Times

The refugees cross the border at night under the protection of rebels, and some of those fleeing arrive wounded by the bullets of the government soldiers trying to stop them, said Andrew Harper, the top official of the United Nations refugee agency in Jordan, in charge of its camps. Some are killed trying to cross.

But since the air assaults picked up about two weeks ago, Syrians have been arriving at a rate of about 2,000 a night, up from about 500 a night before that and hitting a peak of more than 5,000 in just 36 hours about five days ago, making the Zaatari camp here the fastest-growing in any of the three countries housing Syrian refugees.

Nearly half of the refugees here are younger than 12, and women outnumber men almost two to one. Those ratios are expected to grow even more lopsided, Mr. Harper said, because some men deliver their families and return.

Over the last week, hundreds of people have boarded buses back to Syria, most of them men, said aid workers. “Dying there is better than the slow death here,” said Mohamed Salama, pushing for a place on a bus Saturday to the border so he could join the Free Syrian Army.

The Jordanian military keeps about 1,400 Syrian army and police defectors in a separate facility here, with limited chances to visit their families, a common practice to avoid the militarization of the civilian camps.

But at the main Zaatari camp, about 25,000 people remain in a vast city of white tents turned yellow by lashing sand that quickly coats clothes, faces and young lungs with a thick layer of fine dust. Gales and cyclones of sand blow through the endless avenues of tents, and the provision of water, electricity, bathrooms and other amenities still trails the soaring population. Just two small playgrounds serve more than 10,000 children, and there are still no plans for a school or library.