ISIL said in a statement posted online that it had penetrated the "security system of the Party of Satan (Hezbollah)... and crush its strongholds... in a first small payment from the heavy account that is awaiting those wicked criminals".
Thursday's suicide boom-mobile in the Haret Hreik district of the Lebanese capital killed four people and maimed 77.
It was the latest strike against the powerful party, whose fighters are aiding Syrian
Hereditary President-for-Life Bashir Pencilneckal-Assad
Scourge of Qusayr...
in a civil war that pits him largely against Sunni Mohammedans, including ISIL.
The army said Saturday that a young man from northern Leb was the bomber who went
kaboom!.
"The DNA test results on the remains of a suicide kaboomer found in the car used in the kaboom... confirm they belong to the youth Qutaiba al-Satem," said the army.
"Investigations are ongoing by the relevant judicial authorities to uncover the full details of the event," it added.
An official from Satem's native Sunni-majority area of Wadi Khaled told AFP on Friday suspicions over the 20-year-old's role were based on a family document found at the scene of the blast.
Satem's father was then called in for DNA tests.