On Tuesday, as many as 6,000 refugees were waiting to cross into Turkey. About half were in Atmay, a Syrian town near what until a few days ago had been a semi-legal border crossing where Turkish officials were allowing Syrians without passports to enter.

“The people are staying in schools,” said Koteiba, a man who’d tried to cross through Atmay on Monday and said he’d eventually found his way into Turkey illegally through another nearby route.

Koteiba, who declined to give anything more than his first name, predicted that the flow of refugees would only increase as the violence in Syria escalated. He said the city where he lived, Killi, usually was home to about 20,000 people. Only about 5,000 remain, he said.

“Before we could go to the basements, but now they’re using larger bombs,” he said, a reference to the government’s stepped-up use of aircraft to attack rebel positions.

“With the shelling from the tanks, you get a warning when the tanks are coming, and you can move,” he said. “With the airplanes. . . . ” His voice trailed off.

On Tuesday, an example of what Koteiba spoke about was on display in a video of what was reputed to be the aftermath of an airstrike in Kafr Nabl, a city south of Idlib. Activists said the explosion had killed at least 23 people. The video showed burning vehicles and at least five bodies, as well as a crater that had left half the street unpassable. At least two buildings appeared to have been damaged. One military analyst who watched the video said the damage was consistent with a bomb that weighed at least 1,000 pounds.

Koteiba also said sustained fighting had caused cuts in power and fuel and food shortages, another factor in the increasing flow of refugees.

Syrian opposition activists in Reyhanli said they were frustrated by the Turkish decision to prevent refugees from crossing, but they also were careful in their criticisms and quick to point out all the Turkish government has done to support them.

“There are people who have paid to rent apartments for six months or a year. Where are they going to go?” asked one Syrian activist in Reyhanli, who said he’d visited the crossing near Atmay over the weekend to take food and water to the people there. He spoke only on the condition of anonymity because he feared the Turks were cracking down.

The activist said Turkish soldiers along the border had tried to prevent him from taking pictures, but they’d allowed him to deliver the aid.

“They said throw the food and water and then go,” the activist said. “They said they would allow them in by today, but they have not yet.”