By Daren Butler
SANLIURFA, Turkey (Reuters) - Abu Huseyin says he has sent dozens of people from this ancient city in southeastern Turkey to join jihadist groups in northern Syria and vows to continue helping them fulfill what he says is their duty to God.
Several hundred Turks are estimated to be among thousands of foreigners swelling the ranks of Islamist rebels fighting President Bashar al-Assad's forces, generating what some politicians say is a risk that, radicalized and battle-hardened, they could one day return to stage attacks on Turkish soil.
"We send those who are in the path of God for jihad," said Abu Huseyin, a tradesman identified by several locals as a man who helps recruit fighters for Syria from this mixed Turkish, Arab and Kurdish city 50 km (30 miles) from the Syrian frontier.
"Nobody tells these people to go and fight. Most of them meet up in groups of three or five people and make their own decisions to go," he said by telephone, declining to meet in person for fear of jeopardizing his activities.
Turkey has been an outspoken supporter of rebels fighting against Syria's Bashar al-Assad and has assisted them by keeping its border open.
But Turkish opposition politicians have become increasingly alarmed as hardline Islamist groups such as al Qaeda-linked Jabhat al-Nusra and the Islamic State of Iraq and the Levant (ISIL) have risen to prominence among the rebels and taken control of territory in northern Syria near the frontier.
The presence of foreign fighters from around the Muslim world, including Turks, adds to the risk that the conflict will spill beyond Syria, they say, accusing the government of doing too little to fight the threat.
"This is our biggest fear," Mehmet Seker, a member of parliament from the opposition Republican People's Party (CHP) in the southeastern city of Gaziantep, told Reuters. "They received training there. Their thoughts have crystallized. These people could quite easily carry out attacks in Turkey."
Seker is one of several deputies who have called for parliament to launch an investigation into Turkish fighters being recruited for Syria.
The danger of violence hitting neighboring countries was illustrated last week when suicide bombers targeted Iran's embassy in Lebanon, killing 25 people. An anti-Assad Sunni Muslim militant group claimed responsibility.
In Turkey, a bomb attack in May killed 53 people in the border town of Reyhanli, although the authorities say suspects being tried over the attack are linked to Assad, not the Islamist rebels.
Turkish officials strongly reject any suggestion that their opposition to Assad amounts to support for his al Qaeda foes.
"The expression 'love of al Qaeda' was used regarding me personally. No Turkish state minister cultivates special sympathy for al Qaeda or any terrorist group," a furious Foreign Minister Ahmet Davutoglu told a parliamentary commission last week.
Prime Minister Tayyip Erdogan denied this month that Turkey was harboring al Qaeda-linked fighters and said it was fighting against them. Turkish security forces have tightened controls along the 900 km (560-mile) border, seizing a truck loaded with 1,200 rocket warheads and other weapons in the southern city of Adana this month.
Still, Turks are being recruited to join foreign fighters from around North Africa and the Middle East to fight against Assad, often with Islamist groups that openly support al Qaeda.
Pictures on Turkish jihadist websites commemorate Turks who have died fighting in Syria, while videos on You Tube show armed men speaking in Turkish, apparently from inside Syria, calling on their compatriots to join the jihad.
Among those who have been inspired to fight by such images were 20-year-old twins who disappeared from their home in Adiyaman, 150 km from the Syrian border, several months ago when they were due to register at university. Their father, Mehmet, blames Islamists in the town for recruiting them.
"They took my children by force. They brainwashed them. Even if I die I will try and bring them here and watch over them so no harm comes to them," said the retired civil servant, who crossed into Syria in a desperate search for his sons two months ago, tracking them down to a building in Aleppo.
"They refused to show my sons to me and kept them upstairs. When I argued with them they pointed their guns and were going to shoot me so I had to leave," he said, vowing to return.
Britain's ambassador to Turkey, David Reddaway, warned Turks last week about the prospect of militants returning from Syria to carry out attacks.
"Thousands of foreign nationals - including a significant number from the United Kingdom - have joined groups affiliated to al Qaeda (in Syria)," Reddaway wrote in a newspaper editorial marking the 10th anniversary of car bombings in Istanbul targeting the British consulate and local offices of HSBC.
"We are deeply concerned about the potential for these individuals to return to Turkey and other countries in order to carry out attacks."
Al Qaeda claimed responsibility for those 2003 attacks on British targets in Istanbul, which killed 32 people and came a week after car bombs at two Istanbul synagogues killed 30.
Osman Karahan, Turkish lawyer for the convicted Syrian mastermind of the 2003 bombings, was himself killed fighting in Syria last year. He died in a clash with Assad's forces in Aleppo, according to jihadist websites.
A symbolic funeral for Turks who have died fighting in Syria, attended by supporters of Islamist groups, was held at an Istanbul mosque this summer.
The head of the Islamist Ozgur-Der association, involved in supplying aid to Syrians, estimated around 50 Turks had died in Syria among several hundred who had left to fight there.
Speaking in the group's Istanbul offices, Ridvan Kaya said Ozgur-Der itself had not sent jihadist fighters to Syria but that it was not opposed to groups which did, defending them against what he termed "black propaganda" in the Western media.
"We don't think there is a need for fighters there because there are many people in Syria resisting the regime," he said. "But we believe a propaganda war is being conducted against jihadist Islamic fighters."
Parents of Turks who have gone to fight are demanding the state act to prevent more crossing the border. A father from Gaziantep near the frontier tearfully described how his 20-year-old son had fled over the border more than a year ago.
"We would have prevented this happening. I would have found him a wife. I could have sold the house and opened a business for him," he said, declining to give his name.
"But this is not about my son, it's about stopping others from going and I'm concentrating on that. My son has gone and I have lost hope for him."
(Editing by Nick Tattersall and Peter Graff)