The Lebanese authorities are reported to have arrested the head of a jihadist group that claimed the suicide bomb attack on Iran's embassy in November.
Defence Minister Fayez Ghosn told the AFP news agency that Majid al-Majid, the Saudi "emir" of the al-Qaeda-linked Abdullah Azzam Brigades, was being held by army intelligence in Beirut.
Hezbollah's al-Manar television also said Majid was detained "recently".
The embassy attack killed 23 people, including the Iranian cultural attache.
A Salafist cleric close to the Abdullah Azzam Brigades, Sheikh Siraj al-Din Zureiqat, had issued a claim of responsibility in its name.
He warned attacks would continue in Lebanon until Iranian and Hezbollah forces stopped fighting alongside government forces in Syria, and the Sunni group's prisoners were released in Lebanon.