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ISIS flagReuters

An American man born in Iraq was arrested on Thursday for allegedly lying to the FBI about supporting the Islamic State (ISIS) jihadists, after a pledge of allegiance to the group's leader was found on his computer, the Justice Department said.

Bilal Abood, 37, of Mesquite, Texas, is believed to have traveled from the United States to Syria through Mexico and Turkey in 2013, the Justice Department said, according to a report by AFP.

Upon his return four months later, he allegedly told the FBI that he intended to fight alongside the Free Syrian Army to overthrow President Bashar Al-Assad. He also said he stayed in a camp with the rebels.

"He denied ever providing financial support to Al-Nusra Front (ANF), the Islamic State of Iraq and the Levant (ISIL) or any other terrorist organization," said the Justice Department, using another acronym for ISIS.

The FBI reviewed Abood's computer in July 2014, and the Justice Department said investigators discovered an "oath" to ISIS leader Abu Bakr al-Baghdadi.

Authorities said they found that "Abood had been on the Internet viewing ISIL atrocities such as beheadings, and had used his Twitter account to tweet and retweet information on al-Baghdadi," the statement said.

When FBI agents returned his computer this year, Abood said he knew it was a crime to lie to the FBI and denied pledging allegiance to the ISIS leader.

A criminal complaint charged him with "making a false statement to the FBI," the Justice Department said Thursday.

A month before departing for Syria in April 2013, Abood had been denied permission to leave the United States at Dallas Fort Worth International Airport.  At that time, he told authorities he intended to travel to Iraq to visit his family before saying he wanted to fight for the rebels.

He could face a maximum sentence of eight years in jail and a $250,000 fine, noted AFP.

Abood, a naturalized American citizen, migrated to the United States in 2009.He appeared in a federal court in Texas Thursday.

His arrest comes just one day after a 44-year-old American man was sentenced to more than 20 years in prison after he pleaded guilty to supporting ISIS.

The extremist group known for its brutality has motivated a number of supporters in the United States with its radical ideology. U.S. officials said an attempted attack in Texas earlier this month was "inspired" by ISIS, although the group claimed responsibility for the attack.