BEIRUT — An Al Qaeda-linked group claimed responsibility on Saturday for a suicide car bombing last week in a Shi’ite-dominated neighborhood in Lebanon, as its fighters fought other rebels in neighboring Syria in the most serious infighting since the uprising began.
It was the first time that the Al Qaeda-linked Islamic State of Iraq and the Levant claimed responsibility for an attack in Lebanon, underscoring how the ever more complex Syrian war is increasingly spilling over into its smaller neighbor.
The group may have rushed to claim responsibility to try to divert attention from the infighting in Syria, said Aymenn al-Tamimi, an expert on the country’s militant groups.
At least five people were killed in the Thursday attack that targeted a south Beirut neighborhood that is bastion of support for the Shi’ite group Hezbollah.
The Islamic State of Iraq and the Levant vowed more attacks. It was ‘‘the first small payment of a heavy account which these criminal hypocrites should wait for,’’ it said in a statement, referring to Hezbollah. The statement was posted on a website used by Sunni militants.
The Al Qaeda group sought to punish Hezbollah — and their Shi’ite Lebanese backers — for sending fighters to Syria to shore up forces of the President Bashar Assad, who is trying to quell an armed uprising.
The bombing was the latest in a wave of attacks to hit Lebanon in recent months. The violence has targeted both Sunni and Shi’ite neighborhoods, further stoking sectarian tensions that are running high as each community in Lebanon lines up with its brethren in Syria on opposing sides of the civil war.
Meanwhile, the leader of the Abdullah Azzam Brigades, an Al Qaeda-linked group that carried out attacks across the Mideast before shifting its focus to Syria’s civil war, died Saturday while in custody in Lebanon, the army said.
In a short statement, the Lebanese army said Majid al-Majid ‘‘died this morning while undergoing treatment at the central military hospital after his health deteriorated.’’
A Lebanese army general said Majid died after suffering kidney failure.