Parents in Turkish town of Adiyaman tell of anguish of searching for offspring recruited for jihad in neighbouring country

Fatih Yildiz never thought that one day he would have to plead with al-Qaida commander for the lives of his two sons. After a frantic week of searching for them in the blasted ruins of northern Syria, the retired Turkish government official was at his wit's end.

"I swear, if I had had a gun I would have shot that man," Yildiz told the Guardian.

The problem was that the commander – a fellow Turk from Trabzon on the Black Sea coast – could not understand why he wanted his sons back.

"They are here to be martyred," the jihadi leader yelled at Yildiz, who had tracked down his sons to a training camp near Aleppo. "Are you an infidel to try and take that from them? They will be rewarded in paradise."

As the anger welled in Yildiz, 20 Islamist fighters trained their AK-47s on him. "If it had not been for my guide, I would have been killed," he said.

Yildiz neither saw nor spoke to his sons, both in their early 20s. He is one of scores of parents in south-eastern Turkey whose children have vanished across the border to join the Islamist campaign against the Assad regime. Hundreds are thought to have been recruited by units affiliate to al-Qaida.

According to Turkish media reports, young men – and sometimes women – from across Turkey have left to fight in Syria. One newspaper estimated that around 500 Turkish nationals are with Syria's armed opposition.

Parents from Adiyaman, Yildiz's home town, accuse the police and the authorities of turning a blind eye to jihadi recruitment campaign.

"I am starting to be afraid for my son," said a shopkeeper, who did not want to be named. "I've started calling him two or three times on his way to and from school. I call him when he goes out with his friends. I want to know where he is meeting them, and who is coming. Because how can we be sure that they don't get targeted?"

One mother recounted how her 18-year-old son's behaviour shifted radically after he started keeping the company of "a certain group of young men" in Adiyaman. He vanished and has been in Syria for more than six weeks.

"Suddenly my son started to ask me to cover myself in the black charshaf. He told me that my white, thin headscarf was sinful, because it allowed other men to glimpse my hair," said Ayse Demir.

Her brother-in-law, a taxi driver in Adiyaman, also lost a son to jihadists. "He told us that he was going to study in Cyprus. He took 10,000 Turkish lira and left. He called from Syria once."

Under increased international pressure, Ankara has recently insisted that it is not sponsoring extremism in Syria. Sixteen people were arrested in recent crackdowns on al-Qaida-affiliated groups in Turkey. The country froze assets of several hundred individuals and organisations with suspected ties to the terrorist organisation last month.

"In the light of human rights abuses by elements of the armed opposition, Turkey needs to take all necessary steps to investigate and prosecute these people if they pass through Turkish territory," said Emma Sinclair-Webb, senior researcher for Turkey at Human Rights Watch. An HRW report demanded that Turkey "restrict entry of fighters and arms flows to groups credibly found to be implicated in systematic human rights violations". Diplomats interviewed for the report, published in October, voiced concern about the increasing transit of EU nationals and others through Turkey into Syria.

About 200 young men from Adiyaman have joined jihadi groups fighting in Syria, according to some estimates.

"Nobody wants to talk about it," said Yildiz. "Everybody is afraid. They are afraid of al-Qaida. They are afraid for their children. They are afraid that their sons might get arrested by the Turkish police. Some even condone the idea of martyrdom."

Yildiz points to the case of one young man who recently returned from fighting in Syria to his village in Adiyaman province because of an injury. "I went to see them, because I hoped to find out something about my own children. But they would not even let me talk to their son. They were scared that al-Qaida might punish him."

Ali Kara, from Diyarbakir, the main city in south-eastern Turkey, has made seven trips to Aleppo, desperately seeking to learn the fate of his son.

"He told me nine months ago he was going to work in a factory," Kara said. "He called me every week, told me he was at work. Then the calls stopped."

Kara asked one of his son's friends what had happened. "He told me that my son was martyred in Syria. It was a terrible shock."

Kara travelled to the Turkish border town of Kilis, found a trafficker to take him to Syria. "I went from camp to camp, from group to group, looking for an answer." He still does not know if or where his son died.

Yildiz went through a similar ordeal.

Through a connection with Turkish intelligence, he learned that his two sons had crossed into Syria, and with the help of a trafficker made his way to Aleppo. He drove around the war-torn city for more than a week, searching.

"I handed out photographs of my children to the al-Qaida commanders in the city, one at each of their bases. I wandered the streets looking for them. In the end, everybody came to know me as that Turkish guy, looking for his sons."

Some of the fighters were kind, others aggressive, Yildiz found.

"There were many Turks there. But also Chechens, Algerians, Libyans and Europeans."

When Yildiz found the right camp, he was told that men "currently undergoing training" are not allowed visitors.

"They receive weapons training for 45 days. They teach them how to use guns and grenades," he said. "Some are educated to be suicide bombers."

Yildiz said the recruiters use DVDs and video clips on the internet to convince young Turkish men to join jihad in Syria. He was shown a similar DVD in the camp in Aleppo, where a local commander tried to convince him to join his sons.

"There was clip after clip of men committing atrocities, murder and rape. But it was hard to tell who these men were. The commander said: 'Look what the infidels do to our Muslim brothers. We need to defend them.' But they do the same to people in Syria. They kill and torture and rape. What kind of Muslim goes and kills other people? Our religion does not allow this."

Some are worried that Turkey's policy of looking the other way could backfire.

"Right now our government supports anyone who fights against the Assad regime, no matter how brutal they might be," said one Adiyaman neighbourhood elder, who did not wish to be named. "One day they will turn against Turkey, too. They will not stop at the border."

Yildiz agreed. "Many of the people I spoke to in Aleppo told me: 'I'd rather have [President Bashar al-]Assad back than these [fighters]. They have turned our life into hell.' Now they take our children. What will come next? The Turkish government needs to stop this. They need to stop looking the other way," he said.

Riza Firat, another Adiyaman father whose son has vanished, said many jihadists had nothing but contempt for the Turkish government.

"They say [the prime minister, Recep Tayyip Erdogan] is not a real Muslim because he is an ally of the west. Because he does not impose sharia law on Turkey. They call him an infidel."

Firat and Yildiz have started growing beards, hoping to return to Syria as soon as they can raise the necessary money. "Without it, I would not dare to enter any of the al-Qaida camps," said Firat.

Yildiz underlined that his family has always been left-leaning, that four of his daughters went to university.

"In our house we always read the more secular, liberal press," he said. "I just don't understand how my sons could turn to this kind of radical Islam." He swore that he would not give up.

"My sons should be in university now." He added that sometimes people congratulate him on the street. "They tell me I am a great father, and that I will go straight to paradise." He paused. "They don't understand how much I am hurting inside."

• Some names have been changed