At least 23 people were killed and 145 others wounded when two suicide bombers attacked the Iranian Embassy in Beirut on Tuesday, officials said.
The Abdullah Azzam Brigades, a group linked to Al Qaeda, claimed responsibility for the suicide attack.
"It was a double attack in which two of our heroes, Sunnis from Lebanon, sacrificed themselves as martyrs," Sheikh Sirajuddin Zreikat, one of the terrorist group's leaders, said in a Twitter posting.
The brigades threatened to continue staging attacks against Iranian targets in Lebanon until Tehran stopped supporting Syrian President Bashar al-Assad, who is being aided by Iranian fighters.
The Abdullah Azzam Brigades, which was founded in 2009, also demanded that all of its imprisoned members be released by Lebanese officials.
The group, which has claimed responsibility in the past for rocket attacks on Israel, is named for the mentor of late Al Qaeda leader Osama bin Laden and a promoter of international jihad, or holy war.
The two suicide bombers, one driving a vehicle and the other riding a motorcycle, tried to drive into the Iranian Embassy, which is located in the Shiite-majority El Jinah district.
Lebanon has been plagued by sectarian violence involving Sunnis and Shiites since the start of the Syrian civil war in March 2011. EFE