Mejdalaya (Lebanon) (AFP) - When Lebanese authorities announced the arrest last week of three alleged jihadists planning suicide bomb attacks, Elie Warraq's family was stunned to see his name among the accused.

Warraq, 22, would hardly be the only young man in Lebanon lured to the ranks of Sunni Muslim extremists -- but he appears to be the first Christian.

Choking back tears at the family home in the northern Lebanon village of Mejdalaya, Warraq's father Tony said his relatives were devastated.

"We were so shocked when we heard the news, I haven't slept since. It's my son!" Warraq's father Tony told AFP, chain-smoking cigarettes as he sat near a Christmas tree and a table mounted with a small cross.

Warraq's case appears to be the first time in Lebanon that a Christian has converted to Islam and joined a jihadist group.

Lebanon has a complex and fragile sectarian balance and has been struggling with increasing attacks by Islamic extremists.

On Thursday, the Lebanese army announced it had thwarted "a plan to implement a series of suicide attacks" and arrested three people including Warraq, who was going by the name "Abu Ali".

"They were preparing to carry out terrorist attacks against army posts and residential areas and were using falsified Syrian and Palestinian identity documents," the army said.

"The investigation found they had pledged allegiance to terrorist organisations and participated in fighting in Syria and attacks against the army," it added.

It gave no information on which group Warraq and the others had joined or details on their planned attacks.

- 'How do they brainwash them?' -

Warraq's family are well-known devout Christians in northern Lebanon, which has seen increasing jihadist violence, particularly against the army, as the conflict in neighbouring Syria spills across the border.

The family are also army supporters and Warraq's 20-year-old brother Michael is a soldier -- making his arrest even more distressing.

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"I wouldn't wish this on my worst enemy," Tony Warraq said.

"Whenever I see on television that people are blowing up churches and mosques in Iraq and Syria, I wonder 'How could a human do such a thing?'

"But to hear your son is in the same category is very difficult. Am I hallucinating? I still can't believe it."

Warraq initially followed his father into the construction business after finishing high school, and twice worked as a policeman before quitting.

His family says that about 18 months ago, Warraq began to stay away from home for long periods, spending time in the nearby city of Tripoli, where several jihadist groups have a presence.

Despite the absences, Tony Warraq never suspected his son's ideological shift.

"He would go to church on special occasions and holidays," he said.

"He loved music, particularly popular songs, and he would often introduce us to his girlfriends. He was very fond of his dog 'Luc'."

"How do they brainwash them? Do they give them something?" he asked angrily.

- 'Polite and pleasant' -

Warraq's arrest came less than a week after a double suicide bomb attack against a Tripoli neighbourhood killed nine people.

It was claimed by Al-Qaeda's Syrian affiliate, Al-Nusra Front, and was the latest in a string of jihadist attacks in Lebanon.

In the city's Qobba area where Warraq spent time, residents described him as "polite and pleasant".

"He was an introvert. He didn't drink alcohol or smoke," a local mobile phone vendor said.

According to a security source, Warraq twice visited Turkey, where he is believed to have crossed into Syria.

Security services began monitoring him late last year on suspicion that he was transferring arms within Lebanon, passing more easily through checkpoints because he was registered as Christian.

A military source alleged Warraq was planning to become a suicide bomber, but his father insisted that was not possible.

"Maybe he was with a group that was using him because he was Christian, but blowing himself up? Impossible," he said.

Warraq's uncle George said the family could have accepted a conversion to Islam, but not the militancy his nephew allegedly embraced.

"I told him before: 'If you want to become a Muslim, you're free to. But don't get involved in something bad'," the uncle said.

"It's clear that he got caught up in something that there is no coming back from."