More than 45 people were killed and at least 500 were wounded in car bombings in front of Sunni mosques in the northern city of Tripoli last week.
A security source told The Daily Star newspaper in Lebanon one of the suspects, Ahmad Gharib, told his interrogators the attacks were "directly planned by Syrian intelligence." The newspaper said Wednesday he's a suspected member of a pro-Syrian militant group operating from the northern city.
He was identified in video surveillance from near one of the mosques. The source said Gharib made several calls to Syria before last week's attacks.
The Daily Star reports authorities are still investigating the incidents in coordination with the military. Security in Lebanon is tight following the Tripoli blasts and a deadly bombing in a Hezbollah stronghold in southern Beirut.
Hezbollah this year acknowledged it was fighting alongside pro-government forces in the Syrian civil war. The Shiite movement took responsibility for a border explosion that wounded four Israeli soldiers earlier this month.
Lebanon was the subject of an April travel warning from the U.S. State Department. It cited "numerous security incidents" along the border between Syria and Lebanon. Cross-border fighting was reported in Tripoli early this year.