| HALABJA, Iraq
HALABJA, Iraq Twenty-five year old Ako Abd al-Qadir went to wage holy war in Syria vowing to return and conquer all of Iraqi Kurdistan in the name of Islam on the way back to his home town of Halabja.
"God willing, we will come back and trample over your dead bodies until we reach Halabja," he said, threatening the region's "infidel" ruling parties in a video made en route to Syria and posted on social media sites. "Just wait and see".
Ako is one of around 200 young Iraqi Kurds who have joined the ranks of militant Islamists in a conflict that has become a clarion call for home-grown jihadists across the world, keen to prove themselves amid fundamentalist fervor and war.
The trend is alarming for Iraqi Kurdistan, a region that has managed to shield itself from the violence afflicting the rest of Iraq and nearby Syria, and to attract investment from some of the world's largest oil companies.
"Definitely, it's a big concern," said a senior official with knowledge of security issues in the Kurdish capital Arbil, who spoke on condition of anonymity. "The danger is that they will be used as cells to mount attacks on targets here."
Kurdistan is not alone in worrying about jihadi backlash; the roll call of those drawn to the cause of Sunni Islamist rebels battling Syrian President Bashar al-Assad is long and diverse - from veterans of Iraq and Chechnya to young men from London and immigrants from Stockholm.
But the autonomous region's proximity to Syria makes it especially vulnerable. And whilst Kurdistan is used to dealing with external threats, not least along its tightly controlled border with majority Arab Iraq, this one is posed from within.
The region suffered its first major bombing in six years last September, which was claimed by the Islamic State in Iraq and the Levant (ISIL) - a Sunni group also active in Syria.
Publicly, officials in Kurdistan play down the threat and insist that the region will remain safe, but oil companies operating here are taking extra precautions.
"We decided to restrict movements to shopping malls and other high-visibility target areas," said a source at an oil company in Kurdistan. "We're just going to lower our profile a little bit."
"LITTLE TORA BORA"
Famed for its poets and pomegranates, Halabja lies near the mountainous border area between Iraq and Iran, which was once a haven for Sunni militants who formed a group there in 2001 that came to be called Ansar al-Islam.
Ansar al-Islam banned music and forced men to grow their beards in the enclave, named "little Tora Bora" after the Taliban stronghold in Afghanistan where al Qaeda leader Osama bin Laden once sheltered.
Many of the young Kurds who have gone to Syria come from this area, including Ako, who joined Ansar al-Islam as a teenager.
One of the first targets of the U.S.-led invasion of Iraq in 2003 was Ansar al-Islam. By that time, Ako had left the group and handed himself in to the security services because he felt the game was up, according to his friends.
Surviving members of Ansar al-Islam retreated into Iran, but continued to carry out attacks including a twin suicide bombing against Kurdistan's two ruling parties in 2004 that left more than 100 people dead.
Ako served time because authorities considered him to be a danger to national security. After being released from jail, he married and had a daughter. He got a job at an electricity generating plant and was working at a tea house in Halabja until the day he vanished last November.
The rest is played out on Facebook. On December 8, he wrote that he had joined ISIL in Syria and posted the group's black banner on his page. Earlier pictures show him smiling at Halabja's sports club, and he also posted a whole album of photographs of Barcelona football player Lionel Messi.
Despite Ako's history with militant Islam, his friends were shocked when they heard he was in Syria.
"I was very surprised because when he left Ansar al-Islam his views changed dramatically," said a friend of Ako's from school. "Maybe he still had contact with them, or perhaps there is a cell that persuades these youths to go."
It is not clear whether the young men go to Syria on their own initiative or have been recruited and sent there. Mainstream Islamist parties deny involvement. A committee has been set up by the government to investigate the matter.
A spokesman for the Ministry of Endowments and Religious Affairs said preachers at the region's more than 5,000 mosques, who are on the government payroll, were forbidden to incite violence and would be punished if found doing so.
"There is no evidence that any imam has incited people - directly or indirectly - to go to Syria," Mariwan Naqshbandi said. "We have asked the imams to advise worshippers not to go, but unfortunately they haven't managed to discourage everyone."
Kurdish security services however raided 11 mosques one night last December in the city of Sulaimaniyah on suspicion they were being used as recruitment centers, seizing identity papers and laptops. They have not disclosed what evidence they found.
Although Kurdistan shares a border with Syria, most of the young men travel there through Turkey, some via Lebanon, and others southern Iraq. Around 40 have come back to Kurdistan and are now either behind bars because they are considered a threat to national security, or are under close surveillance.
"I went there to be killed following the path of Allah," said one young Iraqi Kurd who returned from Syria because he was convinced the conflict was a western conspiracy to exterminate the world's Muslims.
But many believe these aspiring Kurdish jihadists are driven as much by the hardships of life as by their faith.
Asked why they thought Ako had gone to Syria, his friends and acquaintances all cited economic pressures, and the fact he grew up an orphan in Halabja, better known as the site of a 1988 chemical weapons attack under Iraqi dictator Saddam Hussein.
The Kurds' fortunes have since changed, and their region is now Iraq's most stable and prosperous, but the people of Halabja often complain of neglect.
"The KRG (Kurdistan Regional Government) will need to focus on using its oil wealth to increase opportunities for employment and to reduce corruption if it is to address this threat effectively," IHS Jane's said in a recent report about militancy in Kurdistan, assessing the risk as "serious".
RELIGION VS. ETHNICITY
Ako's jihad lasted less than two months. ISIL announced his "martyrdom" early this year in Syria, killed fighting not Assad's forces but fellow Kurds, who have taken advantage of the civil war to assert control in the country's northeast.
Kurds are predominantly Sunni Muslim, but identify overwhelmingly with their ethnicity - the defining factor in a long history of struggle in the four countries across which they are spread: Turkey, Iran, Iraq and Syria.
ISIL and other Sunni armed groups in Syria have turned their weapons against a Marxist-inspired Kurdish militia that stands in the way of their vision of an Islamic state spanning from Iraq to the Mediterranean.
Wearing a black leather jacket over his Kurdish clothes, the young man who did return from Syria said he would have no qualms about fighting his ethnic kin in the name of Islam: "My religion comes before my Kurdishness - I make decisions based on my religion."
(Editing by Giles Elgood)