Deadly Blast Hits Hezbollah Neighborhood in Beirut BEIRUT, Lebanon - A powerful explosion hit the southern suburbs of Beirut on Thursday afternoon in a neighborhood populated by supporters of Hezbollah, the Lebanese Shiite militia and political party. It appeared to be the latest in a spree of bombings and reprisal bombings over Hezbollah's support for the government of neighboring Syria in that country's civil war. Hezbollah's Al Manar television channel showed scenes of chaos in a residential area, with smoke rising above charred cars, crowds of people pushing past one another and ambulances and fire trucks arriving. The channel said that at least three people had been killed and eight wounded. The blast came six days after a car bomb killed a prominent member of the Future bloc, the Sunni party that is Hezbollah's main political rival. And it came a day after reports surfaced of the arrest by Lebanese authorities of a Saudi militant who leads the Abdullah Azzam Brigades, a group affiliated with Al Qaeda that claimed responsibility for a November suicide bombing at the Beirut embassy of Iran, Hezbollah's ally. The recent bombings are part of a string of escalating attacks in recent months believed related to the nearly three-year-old conflict in Syria, which has deepened Lebanon's pre-existing political and sectarian divisions. Hezbollah backs the Syrian government, sending its fighters to aid the army, and the Future movement backs the insurgency, which Lebanese Sunni militants have crossed the border to join. In a video statement last week, a cleric acting as a spokesman for the Abdullah Azzam Brigades declared that the group would not stop its bombings until Hezbollah withdraws its fighters from Syria and Lebanese authorities release youths imprisoned for militant activities. Lebanese officials had expressed concern after the arrest of the group's leader, Majid al-Majid, about the possibility of retaliatory attacks. Areas in Beirut's southern suburbs, where Hezbollah maintains its headquarters, have been hit twice in the past year, first in July, in a bombing that wounded many but caused no reported deaths, then in August, when a bomb killed at least 18 people and wounded hundreds. The August attack was closely followed by two attacks on Sunni mosques in the northern city of Tripoli that killed dozens. Threats have multiplied against Hezbollah and its followers from supporters of the Syrian insurgency who are incensed that Hezbollah has sent fighters to support the Syrian government in key battles. While the Future bloc officially disavows the use of violence, some of its leaders have been involved in funneling arms to Syrian rebels, and some of its constituents have become radicalized, following hard-line Sunni clerics who have called for attacks on Hezbollah. And insurgents from Syria, including foreign jihadists as well as Syrians, have increasingly penetrated the porous border into Lebanon, and in recent weeks some groups have said in interviews and video statements that they plan to escalate attacks on Hezbollah interests in Lebanon. In an interview last month, a rebel commander said that some insurgent groups had already arrived in Lebanon from Syria. "They want to attack all the regime's allies in Lebanon," the commander said, asking not to be identified by name for protection from reprisals. Lebanon became their arena. In another recent interview, a Syrian anti-government activist reached in Aleppo, the embattled city in northern Syria, said that 125 fighters were preparing to leave the city to launch attacks in Hezbollah's heartland in southern Lebanon, including some fighters from the two most radical rebel groups, the Qaeda-linked Nusra Front and the even more extremist Islamic State in Iraq and Syria. The Aleppo activist, who said he was not involved with either group, spoke on condition of anonymity for fear of retribution. Also last month, a group calling itself Mujahedeen of the Land of Sham, a reference to greater Syria, circulated a YouTube video showing masked youths undergoing military training, in which one fighter read a statement saying that the group planned to shell what it called "Hezbollah strongholds" in the towns of Nubol and Zahra, predominantly Shiite villages in Aleppo province. The video, which has since been removed by YouTube as a violation of its policy on violence, also said the group's attacks on Hezbollah members would be aimed at "making their day night and their night day." Hezbollah's leader, Hassan Nasrallah, has said in speeches that the group is fighting in Syria to thwart takfiris, a disparaging reference to Sunni extremists who brand their opponents as infidels. Mr. Nasrallah has called them a threat not just to Shiites but to the entire region. Mohammad Ghannam and Hwaida Saad contributed reporting.