AMMAN (Reuters) - He had a good job and a loving family, but it wasn't enough for a 25-year old Jordanian who abandoned his life of privilege in Amman to join the Islamic State group that has seized swathes of neighboring Iraq and Syria.
Handsome, courteous and highly regarded in his profession as a radiologist, the man, whose name has been withheld for security reasons, disappeared in early August after the Muslim Eid holiday. He did not tell his family where he was going.
He later called his parents from an undisclosed location to say he had "forsaken his life for the glory of Islam", said a relative. "His father is heartbroken, and his mother is in hospital from shock," he said.
He is among the first known cases of Jordanians joining Islamic State since the group declared a "caliphate" in June after dramatic territorial gains in Iraq and Syria.
His story points to the widening support for Islamic State among Jordanian Islamist fundamentalists inspired by its recent advances in countries that border Jordan to the east and north. With that support come new risks for a U.S. ally mostly unscathed by the Middle Eastern turmoil of recent years.
Jordan's powerful intelligence services appear to be deploying their full range of tools to counter the threat. King Abdullah has said the country has never been better prepared to face the radical threat sweeping the region.
Islamic State's gains have sparked a fierce debate among Jordanian Islamists from the ultra-orthodox Salafist movement on whether to back the group, whose brutality has been criticized even within radical Islamist circles.
But buoyed by territorial gains, Islamic State’s sympathizers appear to be winning the argument.
"Many youths have changed their distorted view of the Islamic State after they saw their actions on the ground, their achievements, and how the West has ganged up against it," a well-known Jordanian militant told Reuters under the assumed name Ghareeb al-Akhwan al-Urduni.
Since the civil war erupted in neighboring Syria in 2011, hundreds of Jordanians have joined a Sunni Islamist-led insurgency against President Bashar al-Assad. More than 2,000 men, ranging from underprivileged youths to doctors and - in one case - an air force captain, have abandoned Jordan for jihad in Syria, according to Islamists close to the subject.
At least 250 of them have been killed there.
But the Islamic State's recent accomplishments are helping to galvanize support like never before among radical Islamists who dream of erasing borders across the Muslim world to establish a pan-Islamic nation.
It raises the prospect of yet more Jordanians crossing the border to fight, but also the risk of Islamic State sympathizers striking in Jordan itself - a country that has suffered Islamist militancy before, notably bomb attacks on Amman hotels by al Qaeda-linked militants during the U.S. occupation of Iraq.
The appearance of Islamic State leader Abu Bakr al-Baghdadi, the self-declared "caliph", calling for the support of Muslims in the pulpit of a mosque in the Iraqi city of Mosul last June acted like a magnet for young Jordanian Islamists.
"Their dream was setting up the caliphate, and now they see it being achieved. This made people consider very seriously joining, especially since the Islamic State had officially invited them," said Bassam Nasser, a Jordanian Islamist scholar.
The roots of Islamic State can, in one sense, be traced to Jordan. It was Abu Musab al Zarqawi, a Jordanian, who founded the Iraqi arm of al Qaeda that would eventually mutate into Islamic State. Al Qaeda has now disavowed the group.
In the impoverished Jordanian town of Zarqa, Zarqawi's birthplace and a traditional stronghold of Islamist fundamentalists, support for Islamic State was on full display during Eid prayers that marked the end of the holy fasting month of Ramadan in late July.
Scores of men dressed in the kind of Afghan-style clothing often worn by radical Islamists waved Islamic State's black flag as they gathered in an open field to listen to Jordanian Islamist Sheikh Amer Khalalyeh praise the group.
"Oh Baghdadi, you who has spread terror in the hearts of our enemies, enlist me as a martyr," chanted the sheikh over a microphone. The footage was captured in a video posted on YouTube.
In the assessment of one senior regional security official, speaking on condition of anonymity, Jordan could be home to "hundreds if not thousands of potential sympathizers" who could turn into "potential sleeper cells and time bombs".
The roots of radicalisation in Jordan mirror those commonly cited as its primary cause across the Middle East and include a lack of political liberty and economic opportunity.
King Abdullah, a steadfast U.S. ally who has safeguarded his country's peace treaty with Israel, is seeking to ease concerns in Jordan about the threat posed by Islamic State.
"I am satisfied with the preparations of the armed forces and security agencies. We had planned for surprises several months ago and we were ahead of others. I can assure you -politically, securitywise and militarily our position today is stronger than in the past," he told politicians.
In an indirect reference to Islamic State, he warned Jordanians not to fall prey to outside parties seeking to exploit their grievances.
In recent weeks, the Jordanian intelligence services have tightened security around sensitive government areas, stepped up surveillance of Islamist fundamentalists and arrested activists seen as a threat, diplomats and officials say.
At least a dozen people have been arrested for expressing support for Islamic State on social media.
It is a new test for the Jordanian security services, which have been a major U.S. partner in fighting radical Islamists.
Jordan's approach to confronting the risk has set it apart from some other Arab states. Its dependence on sophisticated intelligence gathering rather than arbitrary arrests have been credited for sparing Jordan the kind of vendetta-fueled Islamist insurrections seen in states such as Egypt and Syria.
The authorities last month released a prominent Islamist scholar, an influential figure in militant circles, who is one of the leading Islamist opponents of Islamic State.
Sheikh Abu Mohammad al Maqdisi's release has added an influential voice to the debate, but also revealed divisions among Jordan's previously cohesive hardline Islamist community of ultra-orthodox Salafist Muslims.
Maqdisi has mocked Baghdadi's caliphate and expressed outrage at the brutality unleashed by Islamic State.
"It is giving our jihad a bloody texture that we cannot accept. These images of decapitations are painful. This is something we cannot accept, nor Allah (God). Mercy with the infidels dominated during the spread of Islam," he said this month in an audio message.
That has triggered an avalanche of attacks by Islamic State supporters who have shown none of the deference usually reserved for senior scholars such as Maqdisi. They say he was released not because he had served out his five-year jail term, but with a specific remit to attack Islamic State.
The row has sparked verbal and physical conflict. Two radical Islamists who spoke out against Islamic State's decapitations and indiscriminate killings of Shi'ite Muslims were recently physically beaten by the group's supporters.
Islamic State's black flag was also raised in June by supporters in the historically volatile city of Maan, a tribal stronghold of over 50,000 people about 250 km (156 miles) south of the capital.
Here, crosscurrents of crime, smuggling and tribal disaffection are a combustible mix for the government, which is resented for neglecting the area's development. That has provided fertile ground for Islamist recruitment.
But Mohammad Shalabi, a militant Salafist from Maan who has encouraged Islamists to go to Syria to fight, said Jordan was not a target for Islamic State.
"The Islamic State ... have no interest in targeting Jordan. When I have not consolidated my presence firmly enough in Iraq and Syria I cannot move to Jordan," said Shalabi, also known as Abu Sayyaf. He spent 10 years in prison for militancy including a plot to attack U.S. troops in Jordan.
Shalabi, a respected figure by locals in the city who mediates with tribal chiefs in disputes with the authorities, said his followers had no interest in destabilizing Jordan, unless the government provoked them. "If we felt, God forbid, that injustice is going to befall us or that the circle of injustice is expanding, we will not sit with our hands tied."
Editing by Tom Perry and Will Waterman