BEIRUT, Lebanon — Two powerful explosions struck a busy area in southern Beirut near an Iranian cultural center on Wednesday, killing at least five people and wounding dozens in the latest in a series of bomb attacks on civilians here as violence continued to spill over from the war in neighboring Syria.

The Abdullah Azzam Brigades, an offshoot of Al Qaeda, claimed responsibility, saying it would continue such attacks until the Iranian-backed Lebanese militant group Hezbollah withdrew its forces from Syria, where it is supporting the government’s fight against Syrian rebels and foreign-backed jihadist groups.

“We tell our people in Syria that Iran’s party won’t enjoy security in Lebanon until you restore security in Syria,” the group said in a statement posted on its Twitter account. Until Hezbollah pulls out of Syria and Sunni militants are released from Lebanese jails, it said, “we will continue targeting Iran and its party in Lebanon in their security, political and military bases.”