ONCUPINAR, Turkey -- The Turkish border crossing of Oncupinar, an hour's drive from the embattled Syrian city of Aleppo, is a chaotic buzz of people waiting to pass into one of the most violent regions in the world. Border guards stand by with machine guns to prevent Islamic militants from joining the flow, but within their sight smugglers offer to take travelers across for a surprisingly small fee.

One of the men, who claimed to be a former officer for Syrian intelligence, said he charged just over $20 - but was willing to bargain. Abdul-Rauf, who gave only his first name for fear of prosecution for his illegal profession, said he could take clients within an hour and even help them carry their bags a few hundred meters into Syria.

Abdul-Rauf, a thin man in his thirties with a close-cropped beard, asked whether the travelers were headed for territory controlled by pro-Western rebels or by the Islamic State group. When told the latter, he shook his head disapprovingly.

"Why would you want to go?" he asked, drawing a finger across his throat.

Interviews with a half dozen a smugglers at Oncupinar and other border crossings indicate that foreign militants approach them regularly - and that the border is porous, with areas near Oncupinar and the adjacent city of Kilis as the primary illegal crossing points. All spoke to The Associated Press on condition of anonymity because they feared arrest or violence from criminals and militants they help cross.

Some of the smugglers said they avoid people they suspect might be foreign fighters, while others said they don't ask questions.

Turkey, under pressure from its Western allies, stepped up its efforts to disrupt the flow of foreign fighters into Syria to join the Islamic State group, mainly with surveillance of travelers at airports and bus stations. Officials say their primary objective is to prevent foreign fighters from gaining entry to Turkey, with a secondary one stopping those who might want to leave.

They have established special investigative units and have deported hundreds of suspected foreign militants in recent months. But they said the more than 1,250-kilometer (800-mile) border with Iraq and Syria is often rugged and hard to patrol - and that the smugglers often know the contours better than they do.

"The measures that have been active right now will probably decrease all these activities, but bringing it to zero level - that is almost impossible," said Cemalettin Hasimi, an adviser to the Turkish prime minister's office.

Aaron Stein, associate fellow at the Royal United Services Institute, a London-based think tank, said Turkey has done much to stop the flow of foreign fighters into the country: "They are tracking people to the best of their ability."

But he said the efforts are more lackluster at the border.

"You can still get yourself across the border for about 10 bucks and nobody can understand why," he said. "It seems clear that they could be arresting more people."

The smugglers say a crackdown by authorities over the last year has made their work more dangerous, but the border remains porous because of their knowledge of its vulnerabilities and the complicity of some border guards, who can be bribed.

The smugglers told stories about being approached by foreigners they suspect to be Islamic militants. Some said they avoid helping people who are not Syrian or Turkish, for fear of attention by authorities watching for foreign fighters. The stories could not be verified, but the accounts were consistent with one another. All of those interviewed said they had seen foreigners, including Westerners, trying to cross; it was impossible to tell how many were trying to join IS and how many other rebel groups.

One ex-smuggler, who now makes a living exchanging currency and asked to be identified only by his first name, Mustafa, said that late last month, he saw three tall blond men wandering around and approached them to ask if he could help.

Mustafa, an earnest 25-year-old Syrian who wore jeans and a Levi's shirt, said the men were dressed in shorts, sneakers and long shirts and apparently did not speak Arabic. One of them addressed him in English and asked how to get to Islamic State group territory.

"The accent was 100 percent American," he recalled. "I watch movies. His accent wasn't British or anything else."

He told the men about a nearby crossing to Islamic State territory and offered to take them there. They set an appointment to meet, but he said the three men never showed up.

Other smugglers backed his account of an the Islamic State group crossing point close to a refugee camp in Kilis, and also mentioned one further east near the Syrian city of Jarablus. The AP was able to verify separately a crossing point within a kilometer (half-mile) of the Oncupinar border gate, where there is an unmonitored gap in the border fence leading to territory controlled by the Western-backed Free Syrian Army.

Sipping tea in a black leather jacket, sandals and baseball cap in a cafe in Kilis, a smuggler who identified himself as Abu Mohammed said that he avoids foreign clients because undercover Turkish police officers have been leading a crackdown.

Early this month, he said, a Frenchman, his wife and two children approached him. The woman was wearing a hijab, but he could see blond eyebrows and blue eyes. One of the kids was about three; the other a baby.

"He told me he wanted to go to the Islamic State. I turned him away," said Abu Mohammed, a former house painter from Idlib province in Syria. "If you want to smuggle, you only smuggle Syrians."

Abu Mohammed said he also witnessed Turkish police detain two Uzbeks with their wives near the border crossing.

"It was clear that they were Daish," he said, using an Arabic term for the Islamic State group.

He gave his fee as 20 Turkish lira - just under $9. He splits that with a driver, who brings the travelers to a hole cut in the fence. Nothing stops them from bringing light weapons through.

"You can take over, say, five AK-47s in a bag like this," he said, motioning with his hands the size of a normal duffel bag.

As he spoke, another smuggler stood on a terrace with three men sealing a deal to cross the border.

Abu Mohammed said business has become more dangerous because border guards have stepped up their patrols and undercover work - but that the gap in the fence remains open and business continues because some of the border guard officers are corrupt.

"The officer will call the smuggler to tell him that if he has people, now is the time to cross," Abu Mohammed said.

Yilmaz Akinci contributed to this report